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Bridgestone 50-200cc Service Manual

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1. 3 CARBURETION a Float level b Jet needle adjustment c Main jet 4 COMPRESSION a Rings worn b Piston worn c Cylinder worn d Head gasket leak e Stuck rings f Scoring g O ring leak h Rotary valve oil seal leak III ENGINE OVERHEATING The major causes of engine overheating are 1 Improper break in procedure 2 Improper fuel oil mixture 3 Incorrect ignition timing 4 Incorrect park plug in use 5 Spark plug incorrectly gapped 6 Faulty points and condenser 7 Dirt in carburetor 8 Carbon accumulation in cylinder ports 9 Excessively heavy oil in transmission case 10 Tires underinflated brake drag chain too tight A Improper Break In One of the most frequent cases of engine damage due to overheating is improper break in There appears to be some confusion in the field about the necessity of break in because some 2 cycle engines such as chain saws and outboards do not require it IT IS IMPORTANT TO NOTE THAT ALL MOTORCYCLES REGARDLESS OF BRAND REQUIRE ENGINE BREAK IN e All motorcycle manufacturers specify break in periods ranging from 250 to 2500 miles depending upon the type of engine used Friction is greater during break in until rings have had an opportunity to seat and the cylinder wall has acquired a glaze e Bridgestone cycles should be run in for a minimum of 250 miles Sustained high speeds should be avoided for at least 500 miles preferably 1000 miles IMPRESS
2. 1 Install the gear spring into the pump gear 48 2 Assemble the gear case gasket and housing in place and reinstall 3 screws fastening securely 3 Place a small quantity of oil in the gear case housing and reassemble the pump onto the engine but do not install the mounting screws 4 Reconnect the inlet and outlet oil lines a The brass connecting bolt and spring must be used on the inlet line e The spring must be installed first into the pump and then the check ball e NOTE Only a brass connector bolt can be used in this port b The steel connecting bolt and spring must be used only on the outlet line e The check ball is installed first into the pump and then the spring e NOTE Only a steel connector bolt can be used in this port 5 When assembling the oil line onto the rotary valve cover a steel connector bolt must be used 6 Do not over tighten the connecting bolts 7 Install the 2 pump mounting screws and tighten securely 8 Connect the control cable to the pump and check its adjustment e With the throttle completely closed the oil pump outer cable should have 1 16 of an inch of free play at the oil pump cable stop pin Adjustment is made by the cable adjuster located in the cable by the transmission oil filter plug 9 If after adjusting the pump according to the above instructions it appears that it is pumping too much oil without removing the pump loosen lock nut C and turn the adjusting
3. 13 21 Install the clutch assembly onto the countershaft and countershaft collar Rotate the clutch slowly while holding the sprocket stationary in order to engage the drive dogs To positively engage the drive dogs rotate the kick starter shaft When the clutch is properly installed approximately 1 2 inch of the transmission countershaft will protrude through the clutch assembly Fig 20 NOTE On newer models place the thrust spring over the clutch drive gear install the clutch assembly except for the clutch bracket onto the countershaft replace the splined washer and install the clutch bracket 22 With the sprocket stopper in place install the clutch retaining washer and nut and tighten the retaining nut securely on the 90cc engine Bend the tabs of the washer against the flats of the nut to prevent rotation of this nut during engine operation On the 50 and 60cc engines install the clutch retaining spring clip 23 Install the kick starter return spring spring guide and spacer 24 Install the pinion gear onto the crankshaft with the undercut side of the gear facing up With the piston seat in place tighten the pinion gear retaining nut securely Remember that this is a left hand thread 25 Install the 6 clutch springs and reinstall the clutch thrust plate using the 6 thrust plate bolts Tighten them securely 26 If the clutch release push screw has been removed from the transmission cover reinstall
4. Electrical Equipment 1 Head light 2 Tail light 3 Stop light 4 Battery Manual Multi disc in oil 4 speed constant mesh gear amp foot control Primary Hel gr 1 4 05 Gear Box 1st 1 2 92 2nd 1 1 83 3rd 1 1 32 4th 1 1 00 Secondary Chain 1 2 77 Total Gear Ratio Ist 1 32 8 2nd 1 20 5 3rd 1 14 8 Ath 1 11 2 1 810 mm 71 3 in 660 mm 26 0 in 970 mm 38 1 in 750 mm 29 5 in 1 160 mm 45 7 in 130 mm 5 10 in 2 25 17 4 ply 2 25 17 4 ply 22 8 lbs in 28 4 lbs in 63 78 mm 3 07 inch 45 degrees 69 kg 152 lbs 1 72 gal including 0 264 gal reserve Right Hand Right Foot 6V 15 15W 6V 2W 6V 5W exclusively C H P 6V 18W exclusively C H P 6V 8W 6V 2AH Manual Multi disc in oil 4 speed constant mesh gear amp foot control 4 05 2 92 1 83 1 32 1 00 2 54 kA H H bh H Ha 30 0 18 8 13 6 10 3 kA e H Ha 1 810 mm 71 8 in 660 mm 26 0 in 970 mm 38 1 in 750 mm 29 5 in 1 160 mm 45 7 in 130 mm 5 10 in 2 25 17 4 ply 2 25 17 4 ply 22 8 lbs in 28 4 lbs in 63 78 mm 3 07 inch 45 degrees 69 kg 152 lbs 1 72 gal including 0 264 gal reserve Right Hand Right Foot 6V 15 15W 6V 2W 6V 5W 6V 18W 6V 8W 6V 2AH Engine D Type 2 Piston Displacement 3 Bore amp Stroke 4 Compression Ratio 5 Max Brake H P 6 Max Torque 7 Air Intake System 8 S
5. Lights check all lights for proper operation Hd Oo a BW Axle Nuts be certain both front and rear axles are properly secured Cotter pin must be installed in castle nut on front axle 7 Chain check and adjust as required G Steering Damper check for proper operation The damper is intended for use at high speed only Do not overtighten H Idle adjust idle if necessary by visually checking the position of the carburetor throttle valves Adjust cable adjusters on top of carburetors so that with throttle grip closed 1 32 of free play can be felt in the throttle cable at each carburetor I Oil Injection Adjustment the entire oil injection system is designed to provide the correct oil mixture at all speeds The only adjustment it will ever need is the cable adjustment e The oil pump volume is affected by the position of the throttle and varies from 20 to 1 mixture at full throttle to 100 to 1 at idle e To adjust the oil pump control cable proceed according to the sequence as outlined under Oil injection System 175 DT Section B page 51 8 BREAK IN ALL MODELS A First 250 miles The oil injection tank is filled with 2 cycle oil and the fuel tank is filled with 20 1 gas oil mixture Do not exceed 30 miles per hour 40 mph w 175DT for the first 250 miles To insure proper break in and to prevent spark plug fouling for the first 250 miles do not run at any one constant speed e 250 500 miles Fill the fuel tank wit
6. NOTE The B S 175 DT is equipped with the double cams on the brake drum to assure powerful braking performance 1 The play in the brake lever may be adjusted while running with the screw adjuster on the lever or 2 With the adjusting lock nuts on the front panel 3 Because of the double cams on the drum the A and B of cam A arms must be set parallel with 1 lock nuts and turn buckle at all times to prevent uneven brake action Fig 137 REAR WHEEL The rear wheel has the rear sprocket and drive flange on the left side of the machine and the brake on the right side To absorb shocks while running rubber dampers are installed between rear drum and drive flange Removing Rear Wheel Fig mM 1 Lift the machine on its main stand 2 Remove brake rod adjusting nut 3 Remove torque bar from the side of the hub 66 4 Remove rear shaft nut on left side the big nut need not be touched 5 Pull out rear shaft together with chain adjuster 6 Removing rear hub collar wheel will come off the drive flange on the right side Fig 134 e Take out the wheel by leaning the machine to the left Adjusting Rear Brake 1 Rear brake should be adjusted so that brake pedal can be depressed 3 4 inch 1 inches before brake acts 2 To adjust turn brake adjusting nut as required for proper free play Screw in for less play and out for more e Spin rear wheel with transmis
7. b Poor solder connection 3 TIMING a Advanced b Retarded 4 COIL a Defective b Poor connection c Leaking spark plug wire Fig 148 GAP TESTER NO SPARK STRONG SPARK 1 Defective Switch Sharp blue spark easily jumps gap 2 Disconnected Wire 1 FUEL SYSTEM 3 Shorted Condenser a MIXTURE 4 Grounded Points e Carelessly mixed e Wrong oil 5 Defective Coil e Stale or ethyl gas e Incorrect oil pump 6 Shorted High Tension Wire adjustment b CARBURETION Float level Plugged ets Plugged passage Float valve Idle adjustment Needle jet adjustment c ROTARY VALVE e Broken e Incorrectly installed e Altered e Worn 12 B BURNED PLUG e Check spark with gap tester WEAK SPARK Not likely C FOULED PLUG e Check spark with gap tester WEAK SPARK 1 IGNITION a Burned points b Point gap wrong c Condenser bad d Coil defective 13 GOOD SPARK 1 TIMING a Advanced 2 FUEL SYSTEM a Insufficient Oil b Incorrect oil pump adjustment 3 CARBURETION a Jets or passages plugged b Jet needle adjustment c Incorrect main jet 4 COMPRESSION a Cylinder packing b Crankcase packing c Crankcase drain d Magneto side oil seal 5 MILLED HEAD 6 CARBON FOULING a Cylinder head pre ignition b Excessive compression GOOD SPARK 1 FUEL a Mixture too rich b Too much oil from pump 2 AIR CLEANER a Plugged b Not installed
8. Magneto Flywheel Magneto 19 before T D C N G K B 7 AMAL Type VW15SC 20 to 1 gasoline motor oil SAE No 30 0 132 gal in trans case SAE 20 winter or SAE 10W30 all season 85 km h 53 mph l in 8 5 200mpg 20mph at 380km h paved level test road 1 8m 70 8 inch 14 5 sec Stan st 0 200 m Less than 8 m at 35 km h 26 feet at 22 mph Pressed Steel Backbone Telescopic Fork with Hydraulic Damper BS 60 Sport 2 stroke Single Cyl 58cc 3 54cu in 42 mm x 42 mm 1 65 x 1 65 6 70 1 5 6 HP 8500 rpm 0 48 kg m 7500 rpm Rotary Disc Valve Kick Starter A C Magneto Flywheel Magneto 19 before T D C N G K B 8 AMAL Type VW15SC 20 to 1 gasoline motor oil SAE No 30 0 132 gal in trans case SAE 20 winter or SAE 10W30 all season 88 km h 55 mph l in 8 5 176mpg 20mph at 30km h paved level test road 1 8m 70 8 inch 14 0 sec Stan st 0 200 m Less than 8 m at 35 km h 26 feet at 22 mph Pressed Steel Backbone Telescopic Fork with Hydraulic Damper Transmission 1 Clutch 2 Transmission 3 Gear Ratio e Dimensions Weight 1 Overall Length 2 Overall Width 3 Overall Height 4 Saddle Height 5 Wheelbase 6 Road Clearance 7 Tire Size Front Rear 8 Tire Pressure Front Rear 9 Caster 10 Trail 11 Banking Angle 12 Net Weight 13 Fuel Tank Capacity 14 Front Brake 15 Rear Brake
9. Stop light 4 Speedometer lamp 5 Third gear indicator lamp 6 Neutral indicator lamp 7 Battery Front Rear Front Rear Manual Multiple discs in oil bath Dual Transmission selective 4 speed constant mesh rotary or 5 speed constant mesh return by shifting sportshift lever Primary Helical gear 1 3 41 Gear Box Ist 1 2 61 2nd 1 1 67 3rd 1 1 24 Ath 1 1 00 5th 1 0 85 Secondary Chain 1 2 37 Total Gear Ratio Ist 1 21 19 2nd 1 13 50 3rd 1 10 03 4th 1 8 10 5th 1 6 86 1 885 mm 74 2 inch 750 mm 29 5 inch with Standard Western type Handlebar 1 020 mm 40 2 inch 780 mm 30 7 inch 1 235mm 48 6 inch 150 mm 5 9 inch 2 50 18 4 ply 2 75 18 4 ply 1 6kg cem 221bs in 2 0 kg cm 23 lbs in 64 83 5 mm 3 29 inch 45 123 kg 271 lbs 10 L 2 64 US gal Including 1 2 litre 0 317 US gal reserve 1 8 L 3 8 pint Right Hand Operated Right Foot Operated 12 V 35 25 W 12V 8W 12V 25W 12V 3W 12V 2W 12V 2W 12V 6AH I ENGINE DISASSEMBLY amp REASSEMBLY 50 Sport 60 Sport and 90cc models Most service can be performed on the engine without removing the engine from the frame In fact all operations which occur before the actual splitting of the crankcase sections can be accomplished with the engine mounted in the cycle frame For complete engine disassembly it is necessary to remove the engine from the frame This sequence describes the dismountin
10. it from the inside so that the flats of the screws as seen from the outside of the transmission cover are in a relatively horizontal position with the back of the release push screw flush with the inside of the transmission case cover Fig 3 Be certain that the thrust bearing has been liberally coated with grease and inserted into the push screw Fig 21 Fig 21 27 Position the transmission cover gasket on the locating pins Install the rubber O ring on the carburetor inlet adapter which is a part of the rotary valve cover Fig 22 28 Install the transmission case cover by securing all the transmission case cover Screws 29 Turn the engine assembly over and install the neutral light switch gasket and contact With the transmission in neutral gear check to be certain that the contact in the switch cover touches the contact which is installed onto the end of the shift drum shaft Secure the cover 30 Position the magneto armature plate making use of the reference marks which you made prior to removing this assembly Fig 8 Secure the plate with the 3 armature plate screws 31 Reattach the neutral gear switch wire to the switch cover Tighten the wire retaining screw Fig 7 32 Install the flywheel onto the crankshaft and holding the flywheel stationary with the stopper wrench tighten the flywheel retaining nut securely 33 Install the piston pin onto the connecting rod to check for fit It sh
11. ER NEEN wnt 94 TEMPERATURE SE SA NES GA SE ERGER GE GE GEGEE EG EE 83 B Testing the Ignition Coil issie se Es EE se Es es es ee 55 PISTON DISDLACEMENT LLL LLL LLL 83 C Technical Standards ses RR titititi De RE GE EE 55 COMPRESSION RATIO LLL LLL LLL LLL LLL 84 D Jaen Syste EE 55 HORSEPOWER AND TORQUE 85 E Testing the Lighting Col 56 PISTON SPEED 00 c cece eee cence ene eennees 85 Fy Selenium Rectifier ee er EE EE 56 GEAR RATIO ccc LLL LLL 86 G Battery Charging 50 60 gn 56 BOLT TORQUE 00 ccccecceccuccuceuceeeeeeeees 87 ELECTRICAL EQUIPMENT 175 DT 4 57 KEE ses EER EES EE iiir ir i EIE IS EE ID 57 aak ol Lek OE 57 Engine 1 Type 2 Piston Displacement 3 Bore amp Stroke 4 Compression Ratio 5 Max Brake H P 6 Max Torque 7 Air Intake System 8 Starting System 9 Charging System 10 Ignition System 11 Ignition Timing 12 Spark Plug 13 Carburetor 14 Fuel Mixture 15 Transmission Oil Performance 1 Max Speed 2 Climbing Ability 3 Fuel Consumption 4 Min Turning Radius 5 Acceleration 6 Braking Distance Frame amp Suspension 1 Frame Type 2 Front Suspension SPECIFICATIONS BS 50 Sport 2 stroke Single Cyl 50cc 3 15cu in 39 mm x 42 mm 1 53 x 1 65 in 6 60 1 5 2 HP 8500 rpm 0 45 kg m 7500 rpm Rotary Disc Valve Kick Starter A C
12. Remove the shift drum shift fork assembly from the transmission gears and inspect the shift forks for bends or abnormal wear Fig 13 53 Inspect the two transmission shafts and gears to be certain that they are all in good condition Further disassembly of the transmission is not necessary unless one or more of the gears must be replaced If this is necessary carefully note the position of the gears on the shaft before removing them for replacement Fig 14 54 Remove the kick starter intermediate gear which remains in the crankcase half after the transmission shaft assembly has been withdrawn Note that there is a spacer above and below this gear Keep these spacers with this gear to facilitate reinstallation Fig 15 55 Withdraw the kick starter shaft and gear assembly Notice that there is a spacer on the end of this shaft Keep the spacer with this shaft to facilitate reassembly 11 56 Withdraw the crankshaft assembly Notice that spacing shims are used on either side of the crankshaft balance assembly Fig 16 If the same crankshaft is to be replaced keep these spacers on the crankshaft so that the crankshaft end play will not be affected The number and thickness of spacers on this crankshaft varies from engine to engine Occasionally the spacing shims will stick to the crankshaft bearings Inspect the bearings carefully to be certain that these shims have been removed from both the crankcase sections if t
13. Speed 2 Climbing Gradient 3 Fuel Consumption 4 Min Turning Radius 5 Acceleration Standing Start 1 4 mile 6 Braking Distance Frame amp Suspension 1 Frame Type 2 Front Suspension 3 Rear Suspension SPECIFICATIONS 175 Dual Twin 2 stroke Dual Cylinders 177 cc 10 8 cu inch 50 mm x 45 mm 1 97 x 1 77 inch 9 5 1 20HP 8 000 rpm 1 9 kg m 7 500 rpm Rotary disc valve Kick Starter A C Generator Battery 21 1 2 degrees before T D C NGKB 8H AMAL Type VM 17 SC 2 cycle engine motor oil Gasoline 0 8 litre 0 21 US gal in transmission case SAE No 10W 380 in all seasons or SAE No 30 in summer and SAE No 20 in winter Over 130km h 80 mph lin3 55 km l 129 mpg at 40 km h 25 mph on paved flat test road 1 95 m 76 8 inch Under 18 sec 0 400 m Less than 6 m at 35 km h 20 feet at 22 mph Pipe Frame Cradle Type Telescopic Fork with Hydraulic Damper Swinging Arm with Hydraulic Damper Transmission 1 Clutch 2 Transmission 3 Gear Ratios Dimensions and Weight 1 Overall Length 2 Overall Width 3 Overall Height 4 Saddle Height 5 Wheelbase 6 Road Clearance 7 Tire Size 8 Tire Pressure 9 Caster 10 Trail 11 Banking Angle 12 Net Weight 13 Fuel Tank Capacity 14 Oil Tank Capacity 15 Front Brake 16 Rear Brake Electrical Equipment 1 Head light 2 Tail light 3
14. TE The generator fitted to the BS 175 DT is a six pole magnetic inner rotor type AC dynamo The dynamo consists of a rotor into which magnets are cast and a stator consisting of an iron core and wires wound around the iron core The timing gear is fitted on one end of ee the rotor and a cam which operates the contact breakers is fitted on the other end A six pole permanent magnet is contained in the center of the rotor To increase output anisotripic cast magnets which are specially treated for magnetizing are used The principle of the generator is the same as that of a conventional magneto but the stator consists of three coils as shown in Fig 119 so the dynamo generates three phase alternating current T LR ea er Fa Ed DS e kl a Fig 118 Yallow Outstanding features of the magneto type AC dynamo are good resistance to vibration capability for high speed operation etc This type of dynamo is particularly suitable for high speed motorcycles All Bridgestone 175 models after serial No 16G 11761 are equipped with an improved type generator This new style generator is driven by an extra gear and is turning at crankshaft speed rather than 2 crankshaft speed as did the older type NOTE Timing procedure is the same as old style except points for right cylinder are located at the top and points for left cylinder Fig 119 are located at the bottom of the generator 59 E Selenium Rectifier Coil ean Batter
15. WITH THE CLUTCH GEAR THE GENERATOR GEAR IS INSTALLED SO THAT THE PUNCH MARK ON THE GENERATOR GEAR ALIGNS WITH THE CENTER OF THE FIBER IDLE GEAR 40 Install the kick starter shaft return spring Hook the lower end of the spring into the crankcase and hook the upper end of the spring into the countersunk hole in the starter shaft The starter shaft is to be rotated clockwise and held in position while the spring is wound counter clockwise to install it into the hole in the shaft 41 Install the spring cap to prevent the spring from becoming unhooked 23 42 Install the knock pins into the crankcase assembly and place a new gasket over the knock pins 43 Install a new O ring on the carburetor adapter 44 Coat the clutch release screw roller bearing with heavy grease to hold it in place in the release screw Install the transmission cover and tighten the screw securely 45 Turn the engine around so that you face its left side 46 Coat the left rotary valve cavity with oil and install the left rotary valve aligning the letter L stamped on the valve with the pin in the crankshaft 47 Inspect the left rotary valve cover to be certain that the large O ring is in place and that the center oil seal is in good condition 48 Install the left rotary valve cover locating it on the crankcase by means of the pin in the crankcase and the hole in the cover Secure the cover with four short screws The two remaining
16. and the jet needle is controlled by the throttle grip so that when it is opened the gap increases and the flow of gasoline increases and when it is closed the gap decreases and the flow of gasoline also decreases 43 Air which enters through the air jet mixes with the gasoline from the main jet in the needle jet and it is atomized when mixed with the main air flow and flows into the engine 4 Float Chamber The carburetor makes a proper gasoline air mixture according to the throttle opening and engine speed To create this proper gasoline air mixture the supply of gasoline must remain constant The float chamber supplies a constant flow of gasoline to the carburetor Gasoline flows from the tank through the pipe to the carburetor banjo bolt and between the valve seat and valve to enter the float chamber When gasoline enters the float chamber the float moves up to stay on top of the gasoline and pushes the valve closed with the valve arm When the valve touches the valve seat the flow of gasoline stops When gasoline in the float chamber is consumed and the level lowers the float moves down and the float arm no longer presses against the valve allowing it to move away from the valve seat and gasoline to enter the float chamber between the valve and valve seat These procedures are repeated and a constant level of gasoline is kept in the float chamber B Functions of Various Parts 1 Main Jet Main Jet The main jet controls the fuel
17. carburetor caps 17 Reinstall the right hand carburetor and carburetor cover using a new gasket 18 Before operating the cycle perform the following operations A Ignition timing B Fill transmission with 25 ounces of SAE10W30 motor oil C Put one gallon of premixed fuel in the ratio of 20 parts of gasoline to one part of oil into the fuel tank This mixture will lubricate the engine while the oil pump primes the oil lines As soon as heavy exhaust is seen coming from the mufflers the tank may be filled with regular gasoline D Be certain that the oil supply tank is filled with Bridgestone 2 cycle oil Fig 51 CYLINDERS AND PISTONS A Construction and Operation 25 The cylinders of the 30 60 SPT 90 STD 90 T 90 M are of high grade cast iron and accurately finished by honing In the 90 SPT and 175 DT the cylinders are made of aluminum alloy Cylinder walls are honed after hard chromium plating and then porous treated Because the carburetor is encased in the transmission case in the rotary disc valve engine no intake port is required in the cylinder The intake of fuel is controlled by the opening and closing of the rotary valve The exhaust port is located in the forward part and the transfer ports in the right and left sides and rear part of the cylinder The transfer port in the rear part of the cylinder is called the boost port This booster port expels exhaust gas and induces fresh fuel air mixture int
18. check ball closes the inlet port and the outlet check ball opens the outlet port Oil is forced into the crankcase 3 Operation of Worm Wheel Plunger in Relation to AOV Throttle Grip a Slow speed idling Se Check bull spri When the throttle grip is in zero position i e throttle grip is in closed position the rod c contacts the control lever at its lowest position The worm wheel plunger slides to the left arrow a a and the plunger contacts the adjusting screw as Ed Ceaser shown in Fig 98 The distance of shift of the pices Lopes NG plunger to the adjusting screw d is shortened to less than the height of the worm wheel cam a W thereby reducing the volume of oil b High speed wide open throttle controli by Seng ured d Al When the throttle grip is wide open the cam of the control lever contacts the rod c at its highest point thereby shifting the rod c to the right arrow A The distance of shift of the plunger is lengthened and the volume of oil increased B Adjustment The oil pumps used on B S 90 machines are factory adjusted for the proper amount of oil and should never need adjusting The only time adjusting should be necessary is when a customer or an unauthorized personnel may have tampered with the adjustment If the setting needs adjusting proceed as follows Note Use extreme care when making this adjustment and follow these instructions exactly TO REMOVE AND DIS
19. drive assembly and then remove the thrust caution in removing the transmission case spring cover to avoid spilling this remaining oil 38 With the clutch wrench special wrench remove the pinion gear nut from the end of the crankshaft On the newer models this retaining nut can be removed with a socket wrench CAUTION This is a left hand thread The crankshaft can be kept from rotating during the removal of the pinion gear retaining nut if the piston seat is put in place 34 Remove the 6 clutch thrust plate bolts from the top of the clutch assembly Remove the thrust plate Fig 9 39 Remove the pinion gear from the end of the crankshaft 40 Remove the 6 rotary valve cover screws and remove the rotary valve cover 41 To remove the rotary valve disc insert your finger up through the bottom of the fuel inlet port and gently dislodge the rotary valve disc from the crankshaft collar If a screw driver is used to assist in removing the disc use extreme caution to avoid damaging any part of the rotary valve cavity Fig 11 42 Remove the crankshaft collar and locating pin The locating pin may be removed with a needle nosed pliers 43 Remove the washer and spring guide from the kick starter shaft 44 Unhook the upper spring hook on the kick starter return spring by striking the upper end of the spring on the side opposite the spring hook This will pop the spring hook from the hole in the kick starter shaf
20. or retard the timing or clockwise to advance the timing until the light has just gone out and retighten generator position screw and clamp nut Recheck timing by observing the light as the timing bar engages the slot in the crankshaft It should just go out TO CHECK TIMING LEFT CYLINDER 1 Rotate engine by turning rear wheel until left piston is at top dead center as observed through spark plug hole 2 Connect one test light lead to left point condenser lead wire at the condenser The other test light lead is grounded The light is now off 3 Rotate engine backwards by turning rear wheel backwards until the left points close and the test light is on 4 Now hold a slight pressure on the timing bar and rotate the engine forward until the timing bar engages the slot in the crankshaft If the timing is correct the test light will have just gone out at this point 7 i deich wo E E EE A 7 LEFT CYLINDER TIMING ADJUSTMENT 1 If the light did not go out timing slow or retarded or if the light went out before engagement of the timing bar timing too fast or advanced proceed as follows 2 Loosen the 2 point timing plate screws A fig 116 and with the timing bar inserted into the crankshaft move the plate counter clockwise down to slow retard the timing or clockwise up to speed up advance the timing until the light just goes out 7 Retighten screws Recheck timing by rotating the engine and observing light as
21. special tool under the piston This special tool protects the piston during disassembly and it also holds the crankshaft stationary for further disassembly operation Fig 5 25 Remove the piston pin snap rings and remove the piston pin and piston from the connecting rod A suitable piston pin puller must be used in this operation This is provided in the Bridgestone special tool kit 26 Position the engine on the bench magneto side up Hold the magneto stationary with the stopper wrench special tool and using a socket wrench remove the magneto retaining nut and lock washer Fig 6 27 Mount the magneto puller special tool and holding the magneto stationary with the stopper wrench remove the fly wheel magneto CAUTION When mounting the magneto puller on the 90cc fly wheel magneto insert the three attaching screws just far enough to engage two or three threads If these screws are turned in too far it is possible to damage the magneto coils ee ea eer 28 Remove the wire from the neutral gear switch Fig 7 29 Carefully mark the position of the magneto armature plate relative to the crankcase with a prick punch or with a felt marking pen These reference marks will make it possible to reinstall the magneto armature plate in exactly the same position to avoid the necessity of major timing adjustments when 35 Remove the 6 clutch springs 36 Flatten the up turned sides of the bend washer and remov
22. the gear Place it in mesh with the kick idler gear and the kick starter shaft gear and oil the gears Fig 15 4 We are now ready to install the transmission shaft assemblies and the shift drum shift fork assembly Before doing so familiarize yourself with the positions into which the various shafts and the shift drum will be inserted by studying figure 15 e The splined end of the countershaft the shaft with the smaller gears will be inserted through the kick idler gear the gear that is pressed into the countershaft bearing e The end of the drive shaft will be inserted into the kick starter intermediate gear the one which was installed with the spacers above and below it The splined end of the shaft will point up and the small sprocket will be attached to it when the crankcase sections are joined The large diameter end of the shift drum will be inserted into the large hole in the casting located directly above the kick idler gear and the kick starter intermediate gear 5 Align the countershaft and drive shaft gears so that all gears are in mesh Plan your installation of the shafts so that the longer end of the countershaft extends through the bottom of the crankcase section Now insert the shift forks into the slots of the sliding gears of the transmission 6 Holding both shafts and shift drum together as a unit install the transmission assembly into the crankcase half When the shafts have been partially inserted r
23. the oil flow from the oil tank to the pump Whenever a new cycle is serviced the oil supply line to the pump should be removed at the pump and checked for oil flow If a good supply of oil is not available at this line check the tank filter and lines and correct as necessary Oil must flow freely from this line to supply the engine with the proper lubrication ELECTRICAL EQUIPMENT 50 60 Sport 90cc A Ignition System The ignition system consists of a single magneto coil to provide the necessary current a condenser contact breaker assembly an externally mounted dual winding high tension coil and spark plug Contact Breaker The contact breaker assembly is mounted on the magneto armature plate The actuating cam is located on the crankshaft The contact points should be checked periodically If the contact points are rough or pitted replace them When installing new contact points carefully wipe the surfaces with a lint free paper to remove any residue of grease from the point surfaces which will drastically affect the functioning of the ignition system Ignition Timing Incorrect ignition timing can cause problems not directly related to ignition such as poor fuel consumption overheating hard starting when engine is hot spark plug burning or fouling and even extreme engine damage Therefore when diagnosing an engine problem always check and adjust timing first CAUTION Never under any circumstances should an en
24. the timing bar ae engages the slot in the crankshaft It should just go F out Fig 116 EE EE Er EE r B Ignition Coils 58 The ignition coil induces high voltage current supplied by the battery by the operation of the contact breakers The amount of high voltage current induced is determined by the ratio between the number of windings on the primary coil and secondary coil This high voltage current is supplied to the spark plugs The Bridgestone 175 DT has a battery ignition system Twelve volt battery current flows into the primary coil of the ignition coil When this primary current is cut off suddenly by the operation of the contact breaker high voltage current is induced in the secondary coil C Technical Standards The technical standards of electrical components are indicated below DESCRIPTION SPECIFICATIONS 175DT Condenser Capacity in Microfarads 0 25 to 0 30 mfd X Ignition Coil Operating Voltage 12 0 volt X Primary Operating Amperage 1 5 amps each X Ignition Coil Primary Continuity Right Coil White wire to blue wire x 4 5 to 5 0 ohms Left Coil White wire to blue wire x 4 5 to 5 0 ohms Secondary Continuity Right Coil Blue wire to high tension x 9000 to 10 000 ohms Left Coil Blue wire to high tension x 9000 to 10 000 ohms NOTE Refer to Troubleshooting section for proper testing procedures in checking generator and charging system on B S 175 DT D Generator DE
25. the wire from the magneto lighting coil wire to the lighting hot wire V HORN CIRCUIT Connect a light to the hot wire from the battery If it doesn t light check the wiring and the battery charge To check the horn operation ground the horn switch wire If you have current to the horn and it doesn t blow either adjust it or replace it VI SELENIUM RECTIFIER A simple check to see if the rectifier is in good condition is to connect the leads of the continuity tester to the terminals of the rectifier The light should light when the leads are connected one way but it should not light when the leads are switched This is because the rectifier should pass D C current in one direction only If the light lights in both connections the rectifier is defective 175 DT In testing the generator and charging system follow the procedure as listed below to locate the problem exactly and quickly 1 With the engine off connect an amp meter into the circuit of the red wire on the battery at the fuse 2 Start the engine in the day time position of the key switch and observe the amp meter At idle the meter should show a discharge of 2 amps When the engine is run faster 4000 RPM the meter should read 0 No charge or discharge with models equipped with the high low switch and the switch is in high charge position the 0 no charge or discharge will occur at 3000 RPM e When the engine is run from V to full throttle the amp meter shoul
26. y oz of SAE 10W30 motor oil Transmission level oil is hig 144 checked by removing the oil plug located just in front of the kick starter shaft Caution Do not overfill the transmission case 68 6 ADJUSTMENTS A Tire pressure 24 to 26 lbs front 26 to 30 lbs rear B Brakes Check and adjust as described in Owners Manual C Horn Check for proper operation D Lights Check all lights for proper operation E Axle Nuts Be certain that both the front and rear axles are properly secured F Check the chain and adjust as required 7 The engine should now be started and the carburetor adjusted for proper idle speed It should be noted that oil injector pump can be checked by visibly watching the oil flow through the plastic oil line e Note When the throttle is closed and the engine is not operating the oil pump control arm may not return to the stop pin when the throttle is operated The oil pressure in the pump sometimes holds the arm in an open position but operating the kick starter or engine will allow it to return to its closed position 175 DT 1 OIL INJECTION The oil injection system is factory adjusted for proper operation Fill the oil supply tank with 2 cycle oil Be certain to instruct the purchaser to regularly check the oil supply through the glass inspection port Caution It must never be allowed to run dry 2 FUEL Fill the fuel tank with a 20 1 mixture of regular gas and 2 cycle oil 1 quart of oil in 5 gallo
27. 00 km 250 miles O Pd K KM O SECOND GREASING MILEAGE INTERVAL 3 000 km 2 000 miles 3 000 km 2 000 miles 3 000 km 2 000 miles 4 000 km 2 500 miles 3 000 km 2 000 miles 6 000 km 3 500 miles 6 000 km 3 500 miles 3 000 km 2 000 miles 1 000 km 600 miles 3 000 km 2 000 miles 10 000 km 3 000 km 2 000 miles 6 000 km 3 500 miles ONCE EVERY 3000 km 2000 miles CONC OKXKOKROK e PROCEDURE Grease Grease Grease Grease Grease Grease Oil Oil Motor Oil Grease ONCE EVERY 6000 km 3500 miles o OOeOOoe eO eo o 6 000 miles 6 000 miles 220cc of hydraulic jack oil or mixture of 70 parts of Spindle oil SAE 60 to 30 parts of 30 motor oil SERVICE STANDARDS I CYLINDER COMPRESSION STANDARD MINIMUM 50 60 Spt 90 110 P S I 120 P S I 90 P S I 100 P S I 175 DT 120 P S I 100 P S I II PISTON CLEARANCE MAXIMUM MINIMUM 50 60 Spt 005 in 0025 in 90 T 90 M 90 Std 006 in 003 in 90 Spt 003 in 001 in 175 DT 003 in 001 in III RING GAP MAXIMUM MINIMUM 020 in 006 in IV CONTACT POINT GAP MAXIMUM MINIMUM 016 in 012 in V CONDENSER CAPACITY 0 3 uF VI FRONT FORK OIL CAPACITY 50 60 Spt 6 oz Hydraulic Jack Oil 90 642 7 oz Hydraulic Jack Oil 175 DT 7 8 oz Hydraulic Jack Oil VII TRANSMISSION OIL CAPACITY 50 60 Spt 90 21 oz 175 DT 25 oz VIII SPARK PLUG RECOMMENDATIONS STANDARD 50 Spt NGK B 7 60 Spt N
28. 1 240 the battery is probably defective If the gravity is above 1 240 but will drop to below this reading in 24 hours without connecting it in the cycle the battery is defective 13 If both the battery and the charge rate are satisfactory suspect that the customer is running at too slow an average speed and suggest that he operate the cycle in a lower gear to keep the engine turning faster especially for very slow speed city driving 14 In some cases it has been found that a customer may ride with his foot on the brake pedal so that the stop light burns continuously It is recommended that the cycle not be allowed to idle more than the normal amount necessary in operating the cycle These practices help run the battery down and the customer should be instructed against them ALL MODELS Most troubleshooting will involve bulb replacement 1 Head light bulb burned out 2 Tail light bulb burned out 3 Lights on in the speedometer head Check the neutral gear switch by grounding the terminal screw to any convenient ground The neutral gear light should light when the key switch is in the 1 or 2 position It s important that the spring be connected between the break light switch and the pedal If it is necessary to adjust the throw of the brake light switch loosen the two adjusting nuts and move the switch either up or down The horn on the B S machines is located directly below the fuel tank Do not adjust by turning the nut in t
29. 23 F Battery AC current generated by the AC Dynamo is rectified to DC current by the selenium rectifier and charged into the battery All current for operation of the motorcycle flows from the battery The battery should be kept in good condition at all times since electricity for all electrical equipment is supplied by the battery The capacity of the battery is 12 V 6 AH The battery should be checked periodically by the rider or the dealer See charging specifications for all models in opposite column G Headlight The headlight includes a 12 V 35 W main beam and a 12 V 25 W dim beam The battery is the electric source for the headlight Riding will be dangerous at night if obstacles cannot be seen clearly As the headlight of the Bridgestone DT is operated on battery current it remains bright regardless of engine speed and riders can enjoy safe riding at night H Spark plugs NGK B 8H spark plugs are standard for the Bridgestone 175 DT Be sure to use the proper spark plugs as the engine cannot develop 100 percent performance if an incorrect spark plug is used The spark plug is proper for the engine when the spark plug insulator is light brown in color If the insulator is black or 60 carbon accumulates on it use a hot type of spark plug that is one with a smaller number If the insulator has a bleached appearance use a cold type of spark plug or one with a larger number IF PLUG FOULS IF PLUG BURNS SE Geen EASILY Slow
30. ASSEMBLE THE PUMP e Remove the 2 pump mounting screws e Disconnect the pump control cable from the control arm e Disconnect the inlet and outlet oil lines from the pump Caution Care must be used not to lose the balls and springs from the connecting bolts e Remove the pump from the engine e Disassemble the pump by removing 3 pump housing screws and separate the two pump halves Caution Locate the spring in the end of the pump gear so that it does not become lost TO ADJUST THE PUMP 1 Hold the pump in the position shown below and B A revolve the pump gear so that the highest point of its earned edge A is in contact with the stop pin B 2 Loosen the adjusting screw lock nut C 3 Turn the adjusting screw D in clockwise until it pushes the pump gear out just to the point where the stop pin B is just contacting the high point of C the cam A Check by revolving the pump gear while holding it in against the adjusting screw to see that the gear does not move in and out when it D W I moves from the high to the low point of the cam The stop pin B should just touch the high point of the cam when it is revolved 4 When the screw D has been set so that the stop beta pin B is just touching the high point of the cam turn the adjusting screw D out counterclockwise exactly 3 4 of a turn and secure with the locknut C The pump is now correctly adjusted for all driving speeds TO REASSEMBLE THE PUMP
31. BRIDGESTONE OWNER S HANDBOOK amp SERVICE MANUAL 50 Sport 60 Sport 90 90 Trail 90 Mountain 90 Sport 175 Dual Twin from Fourth Printing June 1974 Originally Published by CLYMER PUBLICATIONS World s largest publisher of books devoted exclusively to automobiles and motorcycles 222 NORTH VIRGIL AVENUE LOS ANGELES CALIFORNIA 90004 TECHNICAL HANDBOOK Index TO CHECK TIMING RIGHT CYLINDER 57 SPECIFICATIONS EEN 1 RIGHT CYLINDER TIMING ADJUSTMENT 58 ERR EE 1 TO CHECK TIMING LEFT CYLINDER 58 BO RE EE 1 LEFT CYLINDER TIMING ADJUSTMENT 58 EEN ie 3 Pe der bin Os ese os Ese AAR Ad De N RS GR GE oe 58 1 9 Dual Wat eiert 5 C Technical Standards o14 000002 00000 seeneeercewneeonenesa 59 DING So EE e 59 I ENGINE DISASSEMBLY amp REASSEMBLY T E Selenium Recuuer sorrir siss sitit E ER EE ER EE N 60 DO Sport 60 Sport and 90cc models 0 0 T HEL EE oeae E EO OS DO DEE ER 60 M REASSEMBLY oo essensies nee ds so oe se Ee Ee Ee Ge KY 12 Cal Ta in A coeds cep 60 VER EE EE one ees 15 H Spark DIESE ERGE EG RS EG EG G EER GR RE EG EER DR ER 60 H ENGINE DISASSEMBLY issie ses ese EE seg SG Seg EE 16 HE ENGINE REASSEMBLY osse Ed EE SG EES GEE EE Ed 19 Dry Charged Storage Batteries 61 IV INSTALLING ENGINE INTO FRAME 24 FRONT FORK erter 63 CYLINDERS AND PISTON EE 26 E ass TEER LKUE Ed EE dd Ed Ed de dd EE EE EE 63 A C
32. GK B 8 90 Std 90 Spt NGK B 7H 90 T NGK B 7H 90M NGK B 7HZ 175 DT NGK B 8H IX TIRE PRESSURE 24 26 lbs Front 26 30 lbs Rear X CRANKSHAFT END PLAY MAXIMUM MINIMUM 020 in 003 in XI CLUTCH ADJUSTMENT d 5 8 free play at clutch lever end XII OIL PUMP ADJUSTMENT 90cc w throttle closed oil pump outer cable should have 1 16 of free play before it moves control arm 175DT at maximum open throttle adjustment should allow space of 1 8 between control arm and stop pin XII CHAIN ADJUSTMENT d slack up or down XIV FLOAT LEVEL 50 60 Spt 90 T 90 M 90 Std 25 32 1 32 above 34 15mm carburetor 90 Spt 175 DT 23 32 1 32 under 34 17mm carburetor XV FRONT BRAKE ADJUSTMENT d 34 free play at lever end before brake acts XVI REAR BRAKE ADJUSTMENT 34 1 brake pedal depression before brake acts XVII TORQUE SETTINGS Cyl Head Nuts 125 in lb 140 in lb 175 DT Pinion Gear Nut 250 in lb Clutch Nut 110 in lb 50 60 Spt 120 in lb 90 cc 130 in lb 175 DT Clutch Thrust Plate Bolts 45 in lb 80 Spark Plug 175 in lb DIMM Bolts sic se oe ae Ee 40 in lb 6mm Bolts 60 um lb 8mm Bolts esse 120 in lb 5mm Screws 35 um lb 6mm Screws 35 um lb APPENDIX USEFUL FORMULAS AND TABLES It is often necessary to convert metric to American dimensions or vice versa This chapter
33. Pilot Jet At idling speed or small throttle ies openings the pilot jet controls the op e d KN et flow of fuel mixed with air which enters through the air jet and atomizes the d mixture Mes T Air Screw The air screw controls the flow of air which mixes with the fuel passing through the pilot jet The standard adjustment of this screw position for the various models Pilot Jet is stated below under Adjustment 3 C Adjustment Carburetors on all models are factory adjusted for proper operation Ried nase and idle In the event idle adjustment is necessary proceed as follows Fig 93 1 Run engine for at least 3 minutes in a properly ventilated area Idle cannot be correctly adjusted on a cold engine 2 Turn idle mixture adjusting screw in clockwise as far as it will go CAUTION DO NOT OVER TIGHTEN 3 Turn idle mixture adjusting screw counter clockwise the number of turns indicated below Fig 94 45 MODEL ADJUSTMENT BS 50 60 Sport 1 turns BS 90STD 90D 90T 90M 1 turns BS 90 Sport 1 turns BS 175 DT 1 turns 4 With the engine running adjust idle speed with idle speed adjusting screw A f to the lowest RPM possible without stalling engine T 5 Turn idle mixture screw 1 2 turn in either direction until point is found where idle RPM is highest 6 Re adjust idle speed screw for best idle speed TO ADJUST FLOAT LEVEL 1 Remove float bowl cover 2 Re
34. R CORRECTLY Positive lead to positive terminal negative lead to negative terminal 62 3 Set charger for correct voltage 6V or 12V 4 DO NOT LET FILLED UNCHARGED BATTERY STAND LONGER THAN 12 HOURS BEFORE CHARGING FRONT FORK Operation When a load is applied to the front fork the load is received by the fork springs At the same time oil in the oil chamber flows into the oil control chamber and the load is held by resistance of the compressed oil and air and the shock is absorbed Oil lock bars are installed inside the bottom of the lower fork legs to prevent the fork from bottoming when receiving severe shocks When oil moves through the gap between the piston oil and the oil lock bar shock is absorbed by the resistance of the oil The oil lock bar is tapered so that oil resistance increases as the front fork shortens When the fork lengthens rebound is dampened by oil resistance generated by the oil flow from the oil control chamber through the oil hole to the oil chamber and by the oil flow through the gap between the oil lock bar and the piston oil hole Front Fork Compressed position Maintenance If it is ever necessary to add fluid to the front fork use hydraulic jack oil To insert fluid into the fork remove the upper bridge bolt on the top of the fork tube Do not add more fluid than is required 6 ozs 50 60 Sport 6 7 ozs 90CC 7 5 ozs 175 DT Inne habe To determine the amount of fluid a
35. Speed EASILY High Speed B 8 H B 7 H B 8 HN SSC B 7 HC B 9 H L 58 R L 5 L 56 T CHAMPION Se 175 BT WIKING DIAGRAM Netal Luni i ai l vam po RA Neutral Switch Mg EET eene seg EI ee ET DI teg ga e Head Light Seen gt Tail Lig 12V AR W 254 IZY EW Spark hig MATHATE Dipper Harn Saleh Dry Charged Storage Batteries ALL MODELS The fully charged battery acts as a voltage stabilizer in the electrical system Because the magneto delivers considerably more current than the rated voltage of the system a fully charged battery is essential asa buffer between the current generating source and the various light bulbs on the cycle A discharged battery does not provide sufficient electrical resistance to perform this buffer function and light bulbs will be burned out when they are switched on due to the excessive current reaching them from the magneto or generator through the discharged battery For this reason it is important that the dealer properly fill and charge the battery just prior to delivering the machine 1 Fill the battery to proper level with 1 260 specific gravity electrolyte 61 2 Allow battery to stand for 2 8 hours without charging 3 Inspect liquid level and add more electrolyte if necessary 4 Measure specific gravity with a hydrometer Table 1 indicates the approximate degree to which the battery is charged stated as percent charged and the approximate ampere hours of charge which will be necessa
36. THESE FACTS UPON PURCHASERS 1 Observe maximum break in speeds 2 Avoid fast engine warm up 3 Avoid fast shifting through the gears 4 Avoid overloading e Once a Bridgestone cycle is broken in properly it is the most trouble free machine available as attested to by the number of large rental operators who are discontinuing other makes in favor of Bridgestone B Fuel amp Oil Mixture It is important to use the proper oils and correct mixing ratios Always use a good grade of regular gas mixed with a brand name 2 cycle oil preferably Rockford Motor Oil recommended for air cooled engines Never use special additive oils or high ratio oils 50 1 or 100 1 Always use 15 1 ratio for break in 20 1 thereafter C Incorrect Ignition Timing The next most frequent cause of overheating is excessively advanced ignition timing Because of its importance carefully note and follow the timing procedures TA D Incorrect Spark Plug in Use A spark plug not recommended for use under the particular operating conditions can result in overheating Select the correct plug recommended for this particular model you may be working on E Spark Plug Incorrectly Gapped An incorrectly gapped plug can effect ignition timing The problem is most frequently found when an American made plug is installed The standard equipment NGK plugs are factory gapped within the correct 025 028 range American plugs will almost always be factory set at a wider gap G
37. aft and engages either first gear B or second gear B by means of the drive dogs on the sides of the gear 34 The gears are so installed that the drive dogs on one gear engage the holes in the gear next to it Gears are never installed with drive dogs facing each other Also the respective gears will fit only one shaft properly Hence all gears will mesh and drive dogs will properly engage the neighboring gears 175 Transmission Mechanism in Neutral Gear Position e Sth gear A 2nd gear A 6202 hall bearing 1st gear 3x15 Woodnff key PIN geer 3rd gaor A Kick storter geor A 6304 Ball bearing 6007 Bail bearing 20 Oil seal Drive sprocket Counterthatt Driveshaft AF Driveshaft bushing 15 Thrust washer 5th gear B Kick starter gear B 4th gear B Ist gear B B Fig 64 SES Jrd gear B B Gear Shift Mechanism The Gear Shift Mechanism consists of a shift drum shift fork assembly shift drum pawl and shift arm assembly drum stopper gearshift shaft and shift pedal 1 Shift drum shift fork assembly The shift drum is cylindrical in shape and it has a spiral like groove two in 175DT cut into its surface into which the shift forks are fitted The rotary motion of the shift drum is translated into side to side motion in the shift forks as they move in the spiral groove The shift forks in turn move the sliding transmission gears from side to side thus shifting the various gears in the drive train 2 Shift Dr
38. and rotate the exhaust pipe toward you down and out of the way 14 Remove the two bolts which connect the engine hanger to the front of the engine Loosen the bolt at the top of the engine hanger and swing the engine hanger forward 15 Moving to the left hand side of the machine remove the gear shift lever 16 Remove the magneto cover retaining screws 17 Remove the two hex head bolts from the lower half of the chain case and remove the lower chain case section 18 Remove the left hand battery cover Disconnect the wires running from the magneto to the battery Remove the battery band and remove the battery Locate the chain connecting link and chain connector Dismount the drive chain from the small sprocket Temporarily reconnect the chain to avoid losing the chain connector Pull the magneto wire loom out of the cycle frame 19 Remove the nuts from the engine mounting bolts The nuts are located on the right hand side of the machine Withdraw the engine mounting bolts from the left hand side of the machine 20 Lower the engine out of the frame FPISTUM SEAL 21 Place the engine on the bench and remove the kick starter lever 22 Remove the cylinder head mounting bolts using a 10mm socket wrench 23 Using a 10mm open end wrench remove the four cylinder mounting nuts Lift the cylinder off the cylinder mounting studs AIr CEA WERE P 24 As soon as the cylinder is removed insert the piston seat
39. ap should be set before installation F Faulty Points and Condenser Check point surfaces for wear Check condensers against specifications as set forth under Electrical Equipment Technical Standards page 59 G Dirt in Carburetor This condition obstructs fuel flow and results in running too lean a mixture which causes overheating H Transmission Oil Too Heavy Excessively heavy oil in the transmission case causes the engine to overwork due to extra drag The transmission should be filled with the correct amount of S A E 10W 30 motor oil I Tires Brakes Chain These items must be periodically checked to avoid placing an abnormal load on the engine due to drag TROUBLESHOOTING TRANSMISSION I MISSED GEARS 1 Check shifter arm pawl Are the pawl teeth broken Check the return spring Fig 149 2 Check the shift drum stopper Is the spring stretched 3 Inspect the gears especially low gear B Any burred or B broken teeth Any broken drive dogs a Fig 150 15 4 Check shafts for straightness 5 Check the shift forks Are they bent or broken 6 Check the shift pins end of shift drum Are there any broken or missing TROUBLESHOOTING ELECTRICAL 50 60 Spt 90cc I KEY SWITCH Fig 154 If a grounded test light does not light with the switch in the on position ground the other battery wire If the light goes on the key switch or the wiring to it is defective If th
40. ar clutch countershaft Second Gear A Third Gear A Third Gear B driveshaft and drive sprocket 39 50 60 Spt 90 cc 175 DT In Fourth Gear Position In Fourth Gear Position Fourth gear A Second gearA Fourth Gear The third Gear B remaining in position the Second Gear A slides to the left and the dog teeth engage with the Fourth Gear A The engine power is transmitted in the order of driven gear clutch countershaft Second Gear A Fourth Gear A Fourth Gear B driveshaft and drive sprocket t7s DT In Fifth Gear Position Fifth Gear The Fifth Gear is engaged with driveshaft by shifting Sportshift lever 40 D Gear Ratios Number of Teeth Transmission Gear Ratio Countershaft Drive Shaft 50 60 Spt 90 cc 175 DT Al CARBURETOR A Construction and Operation The Bridgestone rotary valve models are equipped with Amal type carburetors i e those which control both the fuel and air flow The air passing through the air cleaner enters the carburetor venturi The vacuum created in the venturi by this flow of air causes the fuel in the float chamber to be drawn through the main jet needle jet and then through the passage to the fuel inlet port This fuel is mixed with air entering through the venturi The fuel has been atomized by the air entering through the air jet Carburetors are classified according to the size of the venturi The 50 60 Sport models and the 90cc series ex
41. ar A Boll bearing Bail bearing Wosher Counter shalt Drive sprocket Third geor B Ball beoring Second gear B Fourth geer B First gear B Kick idle gear B Fig 67 W Drive shalt Transmission Mechanism in Neutral Gear Position The transmission in the rotary valve engines is of a constant mesh rotary type running in oil In the 50 60 Sport and 90 cc engines the transmission is 4 speed The 175 Dual Twin has a transmission which is both rotary change type 4 speed and a return change type 5 speed made active by a simple flip of a lever The transmission consists of two shafts the countershaft or clutch shaft and the drive shaft The gears on the countershaft are referred to with the suffix letter A for example first gear A The gears on the drive shaft are referred to with the suffix letter B for example first gear B First gear A is a part of the countershaft Second gear A slides on the splined portion of the countershaft Third gear A and fourth gear A rotate freely on the countershaft These three spinning gears transmit power when they are engaged by drive dogs on the gears next to them Fifth gear A on 175 DT is keyed to the shaft Fourth gear B and third gear B are fitted to the splined portion of the drive shaft and turn with the drive shaft Second gear B first gear B and fifth gear B on 175 DT turn freely on the drive shaft Third gear B slides from side to side on the splined portion of the drive sh
42. cept the 90 Sport utilize the 15mm carburetor The 90 Sport and the 175 DT are equipped with 17mm carburetors Because two carburetors supply a mixture of fuel and air to the 175 DT engine it is important that both mance is obtained Fu SE a Different parts of the carburetor control the fuel air mixture for starting and for low speeds medium and high speeds Instructions for each follow 1 Starter System When the carburetor starter lever on the handlebar is pushed the starter plunger is raised by the starter wire 42 Starter lever cryising position Storer Plunger Startar cobla Fuager cop Throttle valve Jat naudle i j A BS VC oe i i d MNeedis it Sishir amuan iba S wel ay ell E Zi EI Muing chomber body Floo naadle EEE Eh ae Re en Ss Wi Float chambar Haadlie sect When the kick starter lever is depressed with the throttle valve closed air induction is generated behind the throttle valve by the engine suction This condition is similar to that created when the choke of a conventional carburetor is fully closed As the throttle valve is closed air is inhaled only through the starter air channel Strong air induction is generated at the fuel jet located at the narrow starter plunger Fuel in the float chamber is metered by the starter jet and moves up the emulsion tube Air is inhaled from the wall of the tube and a rich mixture of air and gasoline is made When secondary air is added to thi
43. ch torque did it produce Torque 14 7 x 5 252 77 204 22 06 foot pounds rounded off 3 500 3 500 PISTON SPEED It is at times desirable to know the maximum speed pistons reach as they move in their cylinders This peak speed is reached when the piston is midway between top dead center and bottom dead center The formula for finding piston speed is Piston speed Stroke length in inches x 2 x rpm 12 Example An engine has a stroke of 2 5 inches What is its piston speed at 5 000 rpm Piston 2 5 X 2 x 5 000 25 000 85 Speed 12 12 2 083 feet per minute GEAR RATIO Gear ratio is defined as the number of revolutions a driving gear makes to turn a driven gear through one complete revolution By convention a 4 to 1 gear ratio is said to be lower than a 2 5 to 1 ratio Note that it is possible to have a gear ratio of less than unity For a pair of gears the ratio is found by dividing the number of teeth on the driven gear by the number of teeth on the driving gear Example 1 There are 27 teeth on the primary drive gear on a certain motorcycle and 60 teeth on the primary driven gear What is its primary reduction ratio Teeth on driven gear 60 Gear ratio Teeth on driving gear 27 2 22 to 1 rounded off Example 2 In a certain transmission there are 27 teeth on 5th input driving gear and 26 teeth on 5th output driven gear What is the gear ratio The same formula works equally well for engine and rear w
44. ch wire turns the clutch release arm so that the adjusting screw pushes the roller and depresses the clutch set thrust plate ball The clutch springs are then compressed so that they do not press the clutch friction plates against the inner plates As the friction plates and inner plates separate the inner plates cease to turn so that engine power is cut off from the clutch hub and transmission countershaft In addition to transmitting engine power the clutch has a large affect on riding comfort so smooth operation of the clutch is necessary for comfortable riding If the clutch drags gear shift operation becomes faulty and gears or the gear change arm can be damaged If clutch slips poor acceleration engine overheating loss of engine power and uncomfortable riding will result C Adjustment Correct clutch operation requires proper setting of both the clutch cable adjuster and the clutch adjusting screw which acts upon the clutch throw out bearing Clutch cable adjustment should not be attempted without first removing the carburetor cover on the right side of the engine assembly The cable adjustment determines the position of the clutch release arm and it is essential that the release arm is properly positioned to assure smooth clutch operation To adjust clutch 1 Remove carburetor cover 2 Turn cable adjuster until the release arm is positioned so that the center to center distance between the release arm pivot pin and the spri
45. connectors use care to avoid losing the ball check valves from the union bolts NOTE The earliest BS175 models were not equipped with ball check valves in the union bolts 5 Remove the two screws which mount the oil pump to the oil pump gear box 6 Remove the four oil pump gear box mounting screws It will be necessary to rotate the pump to remove the last two screws 7 Remove the oil pump and gear box assembly from the rotary valve cover 8 Remove the left hand crank case cover 9 Remove the rotary valve cover CAUTION If it is necessary to pry this cover to remove it from the crankcase use extreme caution Pry only in the area immediately adjacent to rotary valve cover locating pin Prying may cause damage to the crankcase which will result in leaks 10 Remove the rotary valve from the crankshaft Removal can be facilitated by inserting your index finger through the fuel intake port from inside the crankcase and pushing the valve off the crankshaft spline It is not necessary to remove the crankshaft spline 11 Turn the engine around so that you can work on its right hand side Remove the transmission cover mounting screws and the transmission cover 12 Remove the clutch thrust plate by removing the six mounting bolts 13 Remove the clutch springs 14 Place the transmission in any gear Witha small chisel and hammer flatten the bend washer beneath the clutch retaining nut 15 Place the clu
46. contains formulas for doing so with typical examples worked out Also in this chapter are other useful tables and formulas 81 Multiply Volume Cubic centimeters Metric horsepower Brake horsepower Kilogram meters Foot pounds Kilometers per liter Miles per gallon Square millimeters Square centimeters Kilometers per hour Miles per hour Foot pounds Kilogram meters Pounds per square inch Kilograms per square centimeter Miles per hour Feet per minute Miles per hour CONVERSIONS by 0 03937 20 4 0 3937 2 04 0 6214 1 609 3 281 0 3048 0 10 10 0 2 205 0 4536 0 03527 28 35 1 014 0 9859 7 235 0 1383 2 352 0 4252 0 00155 645 2 6 452 0 155 0 6214 1 609 0 1383 7 233 0 0703 14 22 88 0 01136 1 467 82 To obtain Cubic inches Cubic centimeters Gallons Liters Quarts Liters Fluid ounces Cubic centimeters Inches Millimeters Inches Centimeters Miles Kilometers Feet Meters Centimeters Millimeters Pounds Kilograms Ounces Grams Brake horsepower Metric horsepower Foot pounds Kilogram meters Miles per gallon Kilometers per liter Square inches Square millimeters Square centimeters Square inches Miles per hour Kilometers per hour Kilogram meters Foot pounds Kilograms per square centimeter Pounds per square inch Feet per minute Miles per hour Feet per second EXAMPLES OF CONVERSIONS 1 To convert 250 cubic centimeters to cubic inches multiply 250 cubic centi
47. d read 3 to 5 amps of charges If all the above tests are correct the battery will stay charged when the cycle is operated for normal use 3 If in the above test the 2 amp discharge was observed but no charging occurred suspect a faulty key switch and proceed as follows 4 Leave the red wire from the battery to the key switch disconnected and reconnect the amp meter one lead to positive of the battery and the other lead to the red post of the rectifier 5 Restart the engine and test as in 2 If readings observed in this position are correct the key switch is faulty and replacement is indicated If only discharge is observed or very low charge 2 amp charge or less with high low charge switch on or 1 amp rectifier and proceed as follows 6 Remove all wires from rectifier and connect a D C test light battery operated one lead to the black post and then touch the other lead to the yellow blue white post one at a time Now connect the test light in the same manner but reversing the leads to the black post and use the opposite lead to touch the same color terminals In the above test the test light should have burned at all three connections in one test and the test light should not have burned in the other D C current will pass through a selenium rectifier in only one direction If the test light did not burn according to the above the rectifier can be RI considered faulty If this test was normal check the other half of the
48. damage when the machine is operated Dirty or plugged oil lines tanks or filter could prevent the oil flow from the oil tank to the pump Whenever a new cycle is serviced the oil supply line to the pump should be removed at the pump and checked for oil flow If a good supply of oil is not available at this line check the tank filter and lines and correct as necessary Oil must flow freely from this line to supply the engine with the proper lubrication OIL INJECTION SYSTEM 175DT nn en A Construction and Operation Lubricating oil is supplied by an oil pump attached to the left rotary valve cover Oil pump gear B attached to the pump drive shaft is driven by gear A located on the left end of the crankshaft The oil pump Drive Shaft drives the pump plunger through a worm gear arrangement The speed at which the Plunger rotates then is determined by crankshaft RPM There is a 12 1 reduction in the gearing between the crankshaft and the pump drive shaft In addition to being rotated by the pump drive shaft the Plunger moves up and down in the pump body This Fig 97 Pump gear A reciprocating motion is produced by the cam shaped lower end of the Plunger Ad bearing against the Plunger Guide The Plunger is held against the Plunger guide by the spring loaded Differential Plunger which bears against the top of the Plunger The length of the Plunger stroke is determined by the position of the Stop cam in the lower
49. e top of the piston 6 Pistons for the 90 Sport and 173 DT can be distinguished by the T stamped on the top of 173 pistons and no mark on 90 Sport pistons 7 When installing new pistons or cylinders the piston clearance should be checked and adjusted for proper operation Check the piston clearance at the skirt of the piston and just above the ports in the cylinder e Correct piston clearance for cast iron cylinders 002 003 50 60 Spt 0025 004 90STD T M e Correct piston clearance for aluminum cylinders 0015 0025 90SPT 175DT On cast iron cylinders the cylinder can be honed to adjust clearance On aluminum cylinders the piston must be polished to adjust clearance Pistons are identified on top of the pistons as follows SOSP OSP 900 90T WM 175DT Fig 54 a molded TT stamped CRANKSHAFT AND ROTARY DISC VALVES A Construction and Operation When the piston moves up and down in the cylinder from the force of the explosion of fuel air mixture gas the crankshaft converts this reciprocating movement to rotary motion and supplies power to the rear wheel through the clutch and transmission The crankshaft must endure the impact of explosive force and the high temperatures of combustion Crankshaft strength and precision are required to endure continuous high speed operation for long times Crankshaft materials must be selected carefully and machined exactly to prevent twisting cracking offcentering etc Th
50. e amount and direction vertical or horizontal of engine vibration has extreme affect on riding comfort and fatigue of the rider The crankshaft is one source of vibration If the crankshaft is not balanced properly engine vibration will increase Bridgestone crankshafts are designed to give smooth rotation and balanced operation with a minimum of vibration Rotary disc valves are installed between the carburetors and the crankcase and control the supply of fuel air mixture from the carburetors to the crankcase In conventional two stroke engines the fuel air mixture is controlled by the skirt of the piston and port timing the opening and closing of inlet and exhaust ports is limited to before top dead center and after top dead center so that fuel mixture supply is not efficient By using a rotary disc valve the best timing for engine operation can be determined by altering the cutaway of the valve disc so that fuel supply and engine power are increased Carburetor blow back and fuel loss can also be eliminated and engine performance increased tremendously Fig 55 Cross section of rotary disc valve engine 27 Fig 56 Component parts of rotary disc valve Fig 55 Cross section of rotory dist Fig 36 Component parts of rotary disc valve valve engine Deg Od rag _ Zh mend OF ring om aer das volve eiia B Rotary Valve Modification The rotary valves were redesigned early in 1965 to eliminate the steel hub which was forme
51. e clutch in starting the engine This is a decided advantage since it is not necessary to seek out neutral gear in order to start the engine 29 50 Sport 60 Sport and 90cc KICK MECHANISM Piston Crankshaft Cronkshalt collar Pinion gear SET Be Driven gear Kick idle gear A Ve vi Kick idle gear B Ratchet orm Rotchet stopper Kick gear 7 Circlip 15 mm PER Kick return spring Kick spacer e SH Kick pedal ass y 7 74 Fig 61 a i tA l Si ba i As shown in Figure 62 the kick idle gear A meshes with the driven gear kick idle gear B meshes with kick idle gear A and the kick gear meshes with kick idle gear B Since the kick gear is always in mesh with kick idle gear B the force created by turning the kick pedal is transmitted from kick gear through kick idle gear B kick idle gear A driven gear and pinion gear to the crankshaft and starts the engine 30 175DT j gt D EE E Piston a Crankshaft L Driven Pinior Driven gear had i ell Kick slarter gear A Kick starter geor B Kick starter gear C Kick starter ratchet arm Kick starter shoft Fig 62 CLUTCH A Construction Driver geor comp Pressure plote camp Inner plate Friction plate Clutch hub a LIE TENI aps ajs Clutch spring 5x12 Hexagonal bot Se plote l Hexagonal wosher Disengaged 14 Hexagonal nut ie Countershaft ee Boll bea
52. e in the shaft faces up smaller bolts are torqued to 60 inch pounds when the ratchet arm is resting against the ratchet stopper This positioning of the shaft is 23 Install the bearing retainer on the right hand necessary to secure the proper tension on the side of the engine assembly with the three kick starter return spring when it is installed screws provided Be certain that the small thrust washer is in place on the end of the shaft is inserted into 24 Check to be certain that the spacer washer is the boss provided for it in the crankcase on the gear shift shaft assembly and install the shaft onto the transmission case Place the shifter pawl into the shift drum Check it for freedom of movement 25 Install the shift drum stopper Note that a spacer washer is used behind the stopper and the shoulder bolt passes through the drum stopper and spacer and threads into the boss in the crankcase Connect the drum stopper spring and check the drum stopper for freedom of movement 26 Install the right rotary valve Note that the rotary valves are interchangeable and are marked with the letters L and R The 18 Insert the spring clip onto the shaft behind rotary valve on the right hand side of the the ratchet stopper engine is installed so that the letter N is aligned with the pin in the crankshaft Note 21 Left and right sides of the engine are determined by facing the direction in which 30 Locate the two punch mark
53. e light did light before grounding the other wire the key switch and the wiring to it are O K II CHARGING SYSTEM Connect an amp meter in the line so that current passes through it Place the amp meter in the circuit between the battery and the fuse When the key switch is in the Off position no battery drain should be indicated in the amp meter dial When the key switch is turned on without the engine running you should notice a battery drain on the amp meter With the engine running at approximately V throttle a charging rate of about 1 amp should be seen With the engine running between 4 and throttle approximately a 2 amp charging will be found II BRAKE LIGHT SWITCH 76 Connect a grounded light bulb to the hot wire of the switch It should light if the battery is charged and the key switch is O K Now connect it to the other lead from the switch It should light when the brake pedal is pressed If it doesn t the switch is bad If it does light and the brake light doesn t work the probable cause lies in the bulb or in the wiring between the key switch and the bulb IV HEAD LIGHT Connect a test bulb to the headlight wire If with the engine running the bulb will not light when connected to the head light wire check to see if current is reaching the dimmer switch If it is the switch or the wiring to the light is defective If it does not light check the wiring to the key switch Check the key switch itself by jumping
54. e the clutch retaining nut on the 90cc engine after shifting the transmission into first gear Use the shift lever to shift the gears rather than a pliers to avoid damaging the splined end of the gear shift shaft The sprocket stopper special tool must be slipped over the gear shift shaft on the opposite side of the engine and the steel pegs on this special tool are positioned between the teeth of the small sprocket This holds the sprocket stationary enabling you to remove the clutch retaining nut See figure 10 On the 50cc and 60cc rotary valve engines remove the clutch retaining snap ring to remove the clutch assembly the engine is reassembled Fig 8 Ca 30 Remove the three armature plate attaching screws and remove the magneto armature plate 31 Remove the three neutral gear switch cover mountings screws and remove the switch cover Remove the brass contact located under the cover This contact is fitted to the end of the shift drum shaft 32 Turn the engine over so that the carburetor side faces up and remove the transmission case cover screws 37 Remove the clutch assembly as a unit NOTE On more recent models of the 90cc series a thrust spring fits over the drive gear of the 33 With the screws removed carefully remove clutch In these models remove the clutch the transmission case cover CAUTION Some bracket the splined washer lift out the gear oil will remain in the transmission case so use
55. ed on the AC dynamo The AC dynamo is turned through the pinion drive gear driven gear and timing gear The timing gear turns one full revolution when the crankshaft turns two full revolutions The timing gear and point cam are fixed on the dynamo shaft and turn with it The engine of the BS 175 DT is a two stroke two cylinder engine so two explosions occur every time the crankshaft makes one full revolution As the speed of the AC dynamo is one half of that of the crankshaft contact points must supply four sparks for each revolution of the dynamo so two cams and two sets of contact breakers are installed One contact breaker opens each 90 turn of cam rotation and high voltage current is induced in the ignition coil Contact breaker points should be kept bright and smooth If point surfaces are rough or pitted polish lightly and evenly on an oil stone until the surfaces are smooth If points cannot be repaired replace with new ones After polishing wash the point surfaces with gasoline or thinner and wipe dry with a clean cloth Ignition timing e NOTE Do not attempt to adjust left timing until right timing is completed Movement of generator E during right cylinder timing adjustment will change 8 L 8 left timing RE TO CHECK TIMING RIGHT CYLINDER Gel 1 Remove spark plugs 2 Remove left carburetor air pipe 3 Remove point cover from left end of generator and adjust both sets of points to 012 016 at their widest poi
56. end of the Pump Body The stop cam is part of the control arm assembly which is connected by means of a control cable to the throttle grip Piunger Fig 101 50 Differential plunger When the throttle is closed the lobe of the stop cam limits the down stroke of the Plunger resulting in a short stroke This short stroke of the Plunger reduces the amount of oil pumped at idle As the throttle is opened the Control Arm rotates the eccentric Stop Cam so that the length of the Plunger s stroke is progressively increased resulting in an increased volume of oil being pumped to the injectors OIL INTAKE The diameter of the Plunger is slightly larger than the diameter of the Differential Plunger The pumping action takes place in the area surrounding the Differential Plunger in the oil ie r pump body 5 SS e SE As the plunger moves downward in the pump body this area is increased in volume l H E and a partial vacuum is produced The rotation of the plunger as it moves it downward in the pump body allows the inlet hole in the plunger to align itself with S the Oil Inlet leading from the supply tank This is drawn up through the Plunger z and out the hole in its top and into the areas surrounding the Differential Plunger amp F OIL DISCHARGE ce When the rotating Plunger moves UP in the oil pump body the area surrounding the Differential Plunger is decreased in size and the compressed oil re enters the hole
57. ent is made at the cable adjusting screw located above the left carburetor housing directly in front of the generator Loosen cable adjusting screw lock nut and turn adjusting screw in for additional stop clearance and out for less until Vg inch of stop clearance is observed with the throttle at maximum open position CABLE ADJUSTING SCREW LOCK sur NOTE 1 Do not adjust to less than Cc inch clearance 2 When throttle is closed after adjustment the oil pump control arm may not return S ZE T to its closed position and may appear to be ReTTLE Goen THROTTLE faulty However the oil pressure in the fig 107 pump sometimes holds the control arm open when it is operated without the engine running This can be checked by running the engine or operating the kick starter OFEN C Special Attention Pump Modification Bridgestone 175 Dual Twins manufactured after October 1965 are equipped with a modified oil injection pump The new pump is equipped with ball and spring check valves in each of the pump body oil outlets The springs fit inside the union bolts which are unchanged from previous models DISMANTLING OIL PUMP 1 Ball check valves are installed only in the outlet ports Never in the inlet port 2 Ball check valves cannot be installed in the old style pumps that were not originally equipped with them 3 When assembling the unit first install the ball in the outlet port hole Next install the sp
58. er 23 Pull the shift pawl free of the shift drum and remove the entire gear shift shaft assembly Be certain that the spacer is removed with the shaft It sometimes adheres to the crankcase due to oil surface tension Fig 33 24 Remove the kick starter spring seat and the kick starter shaft return spring 25 Remove the three screws from the bearing retainer and remove the bearing retainer 18 26 Remove the AC generator from the top of engine assembly NOTE It is not necessary to remove the generator in order to split the crankcases Fig 35 27 Invert the engine and remove all of the bolts which join the crankcase sections 28 Separate the crankcase sections 29 Remove the crankshaft assembly 30 Remove the transmission clutch shaft 31 Remove the transmission drive shaft If it is necessary to disassemble the gears from the transmission shafts carefully note their positions before any gears are removed so that you will be able to reassemble them in the same order 32 Remove the neutral gear switch cover from the shift drum and remove the contact from the shift drum Fig 36 33 Lift the fifth speed shift fork to the right so that the guide pin spring and spring seat can be removed from the shift fork 34 Holding the neutral switch in place on the end of the shaft remove the transmission selector shaft from the crankcase 35 Remove the oil splash shield from the transmissi
59. eration Fig 12 13 Install the shift drum stopper collar and retaining screw Connect the drum stopper return spring before inserting the retaining screw The collar goes beneath the shift drum stopper Tighten the shift drum stopper pivot screw securely 14 Install the snap ring on the kick starter shaft 15 Using a needle nosed pliers install the crankshaft collar locating pin into the crankshaft 16 Install the crankshaft collar over the locating pin 17 Install the rotary disc valve after coating it and the valve cavity liberally with oil 18 Carefully check the large O ring around the outer perimeter of the rotary valve cover and check the center oil seal to be certain that they are in good condition Fig 18 Install the rotary valve cover and the 6 retaining screws O RING mg Fig 18 19 Install the drive sprocket sprocket washer and retaining nut onto the transmission drive shaft Tighten the nut finger tight Put the sprocket stopper special tool in position and tighten the retaining nut securely Bend the tabs of the washer against the flats of the retaining nut to prevent its loosening while the machine is being operated 20 Install the clutch collar on the transmission countershaft after oiling the collar liberally and checking it for freedom of movement Fig 19 NOTE On newer models the clutch collar is built right into the shaft thereby eliminating it as a separate component
60. from the fitting on the oil pump and plug this oil line with a screw to prevent the oil from draining out of the supply tank 20 Remove the saddle 21 Remove the side cover from the left hand side of the cycle 22 Disconnect the wiring running between the AC generator and the battery These wires are snap connected 23 Disconnect the wires from the terminals on the selenium rectifier The wiring harness can then be pulled free of the cycle 24 Disconnect the master link on the drive chain and remove the chain from both sprockets 25 Disconnect the exhaust pipe clamps and swing the exhaust pipes down clear of the engine 26 Remove the air cleaner 27 Remove the four engine mounting bolts from the mounting plates at the front of frame assembly 28 Remove the lower rear engine mounting bolt 29 Remove the upper rear engine mounting bolt This bolt should be withdrawn with a pliers since all of the engine weight is now bearing against this last bolt 30 Remove the engine from the cycle frame IT ENGINE DISASSEMBLY 1 With the engine placed on a suitable bench remove the cylinder heads and cylinders 2 Remove the piston pin retaining clips and using the piston pin pusher from the Bridgestone Special Tool Kit remove the piston pins and pistons 16 3 Remove the connecting rod needle roller bearings 4 Remove the oil lines from the oil pump CAUTION If the union bolts are removed from the banjo
61. g of the engine from the frame the complete disassembly of the engine and engine reassembly 23mm 21 19 17 AAN est ee En a Impact AN Driver 1 Remove the drain plug from the under side of the transmission case and completely drain the crankcase Replace the drain plug 2 Turn the fuel cock selector lever to the O position to shut off the fuel between the tank and the carburetor 3 Raise the rubber carburetor cap 4 Remove the carburetor cover from the side of the transmission case by removing the phillips head attaching screws 5 Remove the rubber plug from the access port in front of the carburetor enclosure 6 Insert a screw driver through the access aperture and loosen the carburetor mounting bolt Fig 2 7 Disconnect the fuel line from the fuel cock 8 Remove the carburetor from the carburetor adapter and allow it to hang suspended from the throttle cable and starter jet cable LOCK NU ADJUSTING SCREW 9 Remove the clutch release arm lock nut and washer and remove the clutch release arm from the release screw Fig 3 10 Disconnect the clutch cable from the clutch release arm 11 Unscrew the clutch cable adjusting screw completely out of the threaded boss on top of the carburetor enclosure 12 Pull the clutch cable free of the carburetor enclosure 13 Using the special exhaust pipe clamp nut wrench Fig 4 loosen the exhaust pipe clamp nut
62. gine be run with advanced timing There is however no danger in running the engine with the ignition slightly retarded In fact higher RPM and increased performance will be attained if timing is retarded 2 degrees from the factory setting TO SET TIMING 1 Remove the magneto case cover and locate the timing marks One mark is engraved on the side of the flywheel and the stationary mark is a cast pointer on the magneto case cover See Fig 111 2 Rotate flywheel until points are visible through opening in flywheel and timing marks are approximately aligned 3 Connect one lead of an ohm meter and continuity tester to one of the black wires leading from the magneto Connect the other lead to any convenient ground on the machine 4 Position the flywheel timing mark above the magneto case stationary mark Very slowly rotate the flywheel in a counter clockwise direction direction of engine rotation and stop precisely at the point at 53 which the lowest meter reading occurs or at which the continuity tester light dims Note that the ohm meter never reads 0 or the light never goes out entirely because the condenser is grounded This is the point at which the spark plug fires 5 When this point has been located note the relationship of the timing marks to each other The best setting is about 2 retarded from the ignition angle established by the perfectly aligned timing marks The ignition mark is 3 32 below the center of the sta
63. h regular gas only Be certain that the oil injection supply tank is full Do not exceed 40 miles per hour 50 mph W 175DT Continuing to vary the speed during break in will insure for proper break in e 500 750 miles Do not run continuous maximum speed Check the oil injection tank daily Caution Engine will be severely damaged if tank is allowed to run dry e Note A 20 1 gas oil mixture is used in addition to oil injection for the first 250 to insure proper break in and priming of the oil pump B Never run engine at constant speed during break in Run it up to the maximum allowable speed for a minute or two and then back to lower speeds C Clean the spark plugs every 100 miles during break in D Change transmission oil after the first 250 miles and after 750 miles Then change at regular intervals thereafter E Check and recharge the battery after the break in period At slow speeds the battery does not charge at the normal use rates F Check frequently for normal chain stretch and adjust as required 70 TROUBLESHOOTING ENGINE Troubleshooting is a broad category It covers the search for the cause of such complaints as hard starting poor acceleration poor top speed engine missing over heating short spark plug life scoring rough low speed operation and a multitude of other symptoms Regardless of the complaint the best approach to solving any difficulty is a systematic approach which is followed regardless of the nat
64. he center of the diaphragm on the front of the horn The adjusting screw is located on the back of the horn This is the only screw or nut on the horn which should be turned Make certain the battery is filled properly and charged The charge should be checked with a hydrometer 18 Check the fuse Check the charging coil with an ohmmeter according to the specifications under Electrical Equipment Section C page 59 INSPECTION AND MAINTENANCE 1 Periodic Checking 400 km 250 miles ITEM PROCEDURE Front and Rear Brake Play Check Chain Play Check Mufflers and Exhausts Clean Carbon Clutch Play Check Carburetor Operation Check Battery Liquid Check Spark Plugs Check Contact Point Gap Check Air Cleaner Check Cylinder Head Clean Carbon Bolts and Nuts Tighten Fuel Cock Filter Clean Transmission Oil Replace Items marked O should be checked more frequently II Periodic Greasing Periodic greasing with a grease gun and lubrication ITEM Front Brake Cam Shaft Rear Brake Cam Shaft Throttle Grip Pipe Speedometer Gear Box Front and Rear Wheel Bearings Steering Bearings Oil Felt Magneto Cables Chain Stand Tube Front Fork FIRST GREASING 400 km 250 miles 400 km 230 miles 400 km 250 miles 6 000 km 3 500 miles 3 000 km 2 000 miles 6 000 km 3 500 miles 6 000 km 3 500 miles 1 500 km 1 000 miles 400 km 250 miles 3 000 km 2 000 miles 10 000 km 19 AFTER BREAK IN 4
65. he fifth speed shift fork on B S 175 has been modified after serial No 16B04739 The changes include a guide pin in the crankcase a new shift fork and 5 gear B The new shift fork and gear are interchangeable in sets only When installed in old style crankcase the shift fork is not connected to a pin H h Fig 7E First Gear With the First Gear A on the countershaft remaining in position the Third Gear B on the driveshaft slides to the right and the claws engage with the First Gear B Engine power is transmitted in the order of driven gear clutch countershaft First Gear A First Gear B Third Gear B driveshaft and drive sprocket 50 60 Spt 90 cc 175 DT in Fast Gear Position In First Gear Position a GK Second Gear 38 50 60 Spt 90 ce 175 DF In Second Gear Position In Second Gear Position Tae E Second gear D Third gear B Fig FF The second Gear A remaining in position the Third Gear B slides to the left and the claws on this gear engage with the Second Gear B The engine power is transmitted in the order of driven gear clutch countershaft Second Gear A Second Gear B Third Gear B driveshaft and drive sprocket In Third iti In Third Gear Position Gear Position Third Gear With the Third Gear B on the drive shaft remaining in position the Second Gear A slides to the right and engages with the claws on the Third Gear A The engine power is transmitted in the order of driven ge
66. he oil present has caused them to adhere to the bearings Fig T This completes the disassembly operation Wash all parts except magneto armature plate ina cleaning solvent and inspect all bearings and oil seals If it is necessary to replace bearings the crankcase must be heated with a small torch in the vicinity of the bearings to expand it sufficiently to allow the bearing to be removed and replaced When using a torch keep the torch constantly in motion to avoid melting the crankcase castings If oil seals are to be replaced coat them liberally with oil and tap them into place with a small hammer Before beginning the reassembly operation oil all bearings and oil seals thoroughly IT REASSEMBLY All parts installed inside the two crankcase halves are installed into the magneto clutch section 1 Install the kick starter shaft and gear assembly Position the pin on the ratchet arm into the boss provided for it in the crankcase half 2 Oil the kick idler gear assembly thoroughly This gear need not be removed from the transmission case during disassembly as it is pressed into the counter shaft clutch shaft bearing It is very unlikely that this gear will ever be replaced during the life of the engine 3 Reinstall the kick starter intermediate gear positioning the spacers above and below the gear These spacers are identical and can be identified since the hole in the spacer is the same size as the hole in
67. heel sprockets Teeth on driving gear 27 Gear ratio Teeth on driven gear 26 0 96 to 1 rounded off Example 3 There are 15 teeth on the engine sprocket on a certain bike and 49 teeth on the rear wheel sprocket What is the final reduction ratio Reduction ratio Number of teeth on driven sprocket 49 3 27 to 1 rounded off Number of teeth on drive sprocket 15 86 BOLT TORQUE The following table lists nominal tightening torque for various metric thread sizes BOLT TIGHTENING TORQUES Diameter Pitch Millimeters Millimeters Foot pounds Meter kilograms Coarse thread 2 53 3 47 0 35 0 48 4 56 6 37 0 63 0 88 11 6 15 9 1 6 2 2 22 4 30 4 3 1 4 2 39 1 54 2 5 4 7 5 60 0 83 2 8 3 11 5 94 0 130 13 18 130 181 18 25 188 253 26 35 2 53 3 47 0 35 0 48 3 98 5 57 0 55 0 77 9 76 13 4 1 35 1 85 18 4 25 3 2 55 3 5 32 5 44 8 4 5 6 2 53 5 73 8 7 4 10 2 83 2 116 11 5 16 123 166 17 23 166 239 23 33 87 BS175DT g 60 Sport 88 90 Mountain 90 Trail 89
68. hes is obtained between the clutch release arm pivot pin and spring attaching pin Tighten the cable adjusting screw lock nut securely 6 Turn the clutch adjusting screw until approximately 3 8 of an inch of lever free play is obtained The free play is measured at the lever end Tighten the adjusting screw lock nut 7 Install the left carburetor 8 Attach the control cable to the oil pump control arm Bend the tab on the arm to secure the cable 9 Adjust the control cable by turning the cable adjusting screw so that at the full throttle position there is approximately 1 8 inch of clearance between the control lever and the stop pin When this clearance is obtained tighten the cable adjusting screw lock nut 10 Attach the main oil supply line to the center banjo connector on the oil pump You will recall that we previously plugged this line with a screw to prevent oil from running out of the supply tank 11 Install the left carburetor cover using a new gasket 12 Reinstall the drive chain and install the connecting link spring clip so that the open end of the clip faces the direction opposite of the direction chains rotation 13 Reconnect the wiring between the AC generator key switch and rectifier All connections are made color to color 14 Reinstall the saddle 15 Reinstall the air cleaner assembly 16 Reinstall the left rubber carburetor cap and reinstall the ducts leading from the air cleaner to the
69. hten finger tight 5 Loosen the lower bracket bolt to permit proper positioning of the inner tube and then tighten the upper bracket bolt securely Retighten the lower bracket bolt securely tggi A ug sie Lei NO d SE sm CT IT prana er al A ee tiie E Joy Hne O AVPWIOY 10163 HO og deu ajoyo miT Return stroke Compression stroke 64 REAR SUSPENSION The rear suspension system absorbs shocks in a similar manner to the front fork during operation The rear suspension units are installed between the frame and the rear fork The rear fork moves up and down pivoting on a shaft which fits it to the frame KM FRONT WHEEL The front wheel brake is installed on the right side of the machine The speedometer is installed in the hub to keep out water and dust e fron shalt nai Removing Front Wheel w D E 1 Place a supporting block under the engine 2 Loosen axle bracket bolt 3 Remove front torque bar from the hub side 4 Remove front shaft nut p 5 Pull out front shaft wy speedometer Be gear ei 6 Raise front fork slightly and detach wheel Adjusting Front Brake 1 Front brake cable hand lever should be so adjusted to allow a play of d 34 before the brake acts 2 Adjust screw as required for proper free play ig 65 e Screw in for more play and out for less e Lift front wheel and spin to check for brake drag
70. ifting e fe e N Higk Front tread pedal f d pedal tread m a and The transmission in the 175 Dual Twin can easily be Cn AS switched from the rotary change type four speed described above to the return change type five speed with overdrive left by simply moving a sportshift lever NOTE This QO ef sportshift can be moved while in any gear except neutral The gear change system components are installed in the left 5 SPEED crankcase cover so that maintenance disassembling and inspection are easy mn 2 SPEED Fig 72 Bridgestone 175 s manufactured before November 1965 Serial No 16W02913 were equipped with the old style shift drum on which there were two neutral positions As illustrated above right one neutral was positioned between 1st and 2nd gear the other between 4th and 5th gears Fifth gear B is put into play by putting the Sportshift lever in the 5 speed position and depressing the shift pedal Turning the lever positions the guide pin in the 5 speed shift drum groove thus connecting the 5 gear shift fork to the shift drum When the shift pedal is depressed the drive dogs on 5 gear B a free spinning gear engage the drive dogs on the drive shaft thus transferring power from 5 gear A which is keyed to the clutch shaft to the drive shaft Sportshift levar hott Shift t drum Sportshift shaft 3x10 Roller Fork suide B Sportshitt lever Return spring Sportshift lever mechanism T
71. il can On early models the phillips screw should be replaced with a 5x6 hex bolt for easier removal 2 CARBURETOR amp OIL PUMP CONTROL CABLE ADJUSTMENTS Check and adjust throttle cable at the cable adjusting screw on the top of the carburetor If the idle adjusting screw is turned all the way in the throttle cable should be adjusted so that with the throttle closed the outer cable is moved up and down with out moving the throttle valve If the idle screw has been adjusted for e proper idle speed the outer cable should have 1 16 of an inch of free play When the carburetor adjustment has been made the oil pump control should be checked and adjusted With the throttle completely closed the oil pump outer cable should have 1 16 of an inch of free play at the oil pump cable stop before it moves the control arm on the pump from the stop pin Adjustment is made by the cable adjuster located in the cable by the transmission oil filter plug with a 20 1 mixture of regular gas and 2 cycle oil ie E preferably Rockford oil This mixture must be used for the first 250 miles of operation only Thereafter instruct the customer to fill the tank with regular gasoline only m Law 1 3 FUEL On a new cycle the fuel tank should be filled ad I er d 4 BATTERY Fill and charge the battery follow the procedure as outlined under Dry Charged Storage Battery page 61 f 5 TRANSMISSION Fill the transmission case with 21
72. in the top of the plunger and is discharged through the left or right oil outlet The rotation of the Plunger has aligned the oil outlet port in the Plunger with an oil outlet in the pump body These outlets are located 180 apart in the pump body and are ducted to the oil line fittings on the front of the pump Oil outlet Cit Inlet Rotation of plunger The timing of the alternating alignment of inlet and outlet ports in the Plunger is predetermined by the cam shaped lower end of the plunger It is thus seen that oil pump output volume is regulated both by crankshaft speed and throttle setting B Adjustment The entire oil injection system is designed to provide the correct oil mixture at all speeds The only adjustment it will ever need is the cable adjustment The oil pump volume is affected by the position of the throttle and varies from 20 to 1 mixture at full throttle to 100 to 1 at idle To adjust the oil pump control cable proceed as follows Differential plunger M Remove left carburetor cover ge Turn throttle grip to maximum open position 3 Check the oil pump control arm where the cable is connected and note the pin in the oil pump body and 2 stops on the control arm Fig 107 At the maximum open throttle ip 106 position the stop should be within c inch of the stop pin If the stop clearance is open more than C inch or the stop is closed against the pin adjustment is necessary 51 4 Cable adjustm
73. k the condenser whenever the contact points are changed in the event that it might need changing too should it not meet the specifications required Spark Plug The table below indicates the correct spark plugs for the 90cc 50cc Sport and 60cc Sport models MODEL PLUG USE CODE BRAND Bo D BS 60Sport T8ordsd WJooR JGOR STR aa DE AR FA FA Ke KE ls DR Jo He am DEE PT Fee Fi Pd ae did Ee 54 KEY TO USE CODE A Standard plug for break in and normal use B Hotter plug for low speed use and when standard plug fouls easily C Colder plug for high speed use and when standard plug burns easily D Cold plug Standard for competition use E Extremely cold plug for high speed racing Will operate well only at extremely high temperatures Starting may be difficult with this plug Not recommended for normal use Correct gap on all plugs is between 024 027 The spark plug Terminal should be checked at least every 2 000 miles A worn or dirty plug Special cement produces weak spark and causes hard starting low power output irregular rpm and damage to the ignition coil Insulator ok Powder The spark plug should be checked and cleaned periodically with a Wire gasket E 7 Insulator stiff wire brush and gasoline or other cleaning solvent The use of Ba Plua bod an abrasive in cleaning the spark plug is not recommended since Center electrode t A 8 do abrasive particles may be introduced into the combus
74. ke N Number of cylinders R Radius of one cylinder one half of bore R read R squared means R multiplied by itself Example 1 A single cylinder engine has a bore of 70 millimeters and a stroke of 62 millimeters What is its displacement First convert 70 0 millimeters bore and 62 0 millimeters stroke to centimeters by dividing each by 10 which is equivalent to multiplying each by 0 10 This step is necessary so that our answer will come out in cubic centimeters Then using bore and stroke figures expressed in centimeters in the formula R one half of bore 3 50 S 6 20 N 1 D nxR xSxN D 3 1416 x 3 50 x 6 20 x 1 D 3 1416 x 12 25 x 6 20 D 238 6 cubic centimeters Example 2 A 3 cylinder engine has a bore of 60 0 millimeters and a stroke of 58 8 millimeters What is its piston displacement First convert both bore and stroke into centimeters by multiplying by 0 10 R one half of bore 3 0 centimeters S 5 88 centimeters N 3 D nxR xSxN D 3 1416 x 3 0 x 5 88 x 3 D 3 1416 x 9 0 x 5 88 x 3 D 498 75 cubic centimeters Note that the formula will work equally well if bore and stroke are expressed in inches or millimeters If they are expressed in inches the answer will come out in cubic inches The answer will come out in cubic millimeters if millimeters are used in the formula COMPRESSION RATIO To determine compression ratio of an engine it is first necessary to know piston dis
75. left crackcase cover It may be necessary to adjust the position of the oil lines when this cover is installed to be certain that there are no sharp bends in the oil lines 58 Install the cylinder base gaskets onto the two sets of cylinders studs 59 Install the piston pin needle bearings into the upper ends of the connecting rods and oil them generously 60 Install the pistons 61 Install the piston pins retaining clips Make certain that they art securely seated in the grooves provided for them in the pistons 62 Coat the cylinder walls with oil and install the cylinders onto the cylinder studs 63 Install the cylinder head gaskets and cylinder heads When installing the cylinders heads position the heads so that the small key stone trademark on the underside of the cylinder head faces the front of the cylinder Torque the cylinder nuts to 140 inch pounds 24 IV INSTALLING ENGINE INTO FRAME 1 Position the engine in the frame and install the two rear mounting bolts Install the front mounting bolts and attaching plates and tighten securely 2 Install the new gaskets and connect the exhaust pipes to the cylinders 3 Install the clutch cable and cable adjusting screw into the crankcase assembly 4 Install the clutch release arm onto the release screw after connecting it to the clutch cable Connect the return spring to the spring pin 5 Adjust the clutch cable until a center to center distance of 1 inc
76. lready in the fork remove the upper bridge bolt on the top of the fork tube Insert a wire gauge of sufficient length making certain it touches the bottom of the tube Remove Erem fark bast Moin tering 32 Dil mal Outer woe Put the gauge and measure the fluid mark It id ia O should measure 6 V to 7 inches 50 60 Spt 90 or 7 V to 8 inches 175 DT If no gauge is available remove the screw Over tube A at the bottom of the outer tube and drain the fluid Reinsert the correct amount in ounces for the particular model involved as indicated above FRR TOL Fig 124 NOTE The front fork assemblies on the B S 50 Sport model with serial numbers before 13N are sealed units For these units the above instructions are not applicable Loss of fluid would require replacement of the entire inner tube assembly Assembling Front Fork CAUTION When disassembling or assembling the front fork do not tip inner tube or outer tubes This will avoid spilling the oil supply 63 1 To assemble fork place the cover guide over the inner tube so that it rests on the spring 2 Insert the fork assembly into the fork cover until the cover guide appears in the slot in the fork cover 3 Screw Front Fork Tool special tool into the top of the inner tube and pull the inner tube up through the top of the fork cover Temporarily tighten the fork lower bracket bolt 4 Remove the fork tool and install the upper bracket bolt and tig
77. meters by 0 061 250 x 0 061 15 25 cubic inches 2 To convert 0 65 inch to millimeters multiply 0 65 inch by 25 4 0 65 x 25 4 16 51 millimeters 3 To convert 76 kilograms to pounds multiply 76 kilograms by 2 205 76 x 2 205 167 58 pounds 4 To convert 41 miles per gallon to kilometers per liter multiply 41 miles per gallon by 0 4252 41 x 0 4252 17 43 kilometers per liter 5 To convert 50 miles per hour to feet per second multiply 50 miles per hour by 1 467 50 x 1 467 73 35 feet per second TEMPERATURE It is sometimes specified in a service manual to perform a repair operation at a certain temperature such as heating crankcase halves to 150 degrees C before installing bearings There are two basic formulas for converting degrees F to degrees C and vice versa C 5 9 F 32 F 9 5C 32 Example 1 Measurement temperature for the electrolyte in a battery is specified as 68 degrees F What is that temperature in degrees C C 5 9 F 32 C 5 9 68 32 C 5 9 x 36 C 180 9 C 20 degrees C Example 2 A motorcycle service manual specifies that main bearings be heated to 200 degrees C before installing them onto the crankshaft What is that temperature in degrees F F 9 5C 32 F 9 5 x 200 32 F 360 32 F 392 degrees F 83 PISTON DISPLACEMENT The formula for finding piston displacement can be expressed as D nxR xSxN D Piston displacement t 3 14159265359 a constant S Piston stro
78. move float bowl cover gasket 3 Holding carburetor upside down float valve closed measure distance between gasket seat and top of float with a vernier scale Correct distances are as follows Fig ga MODEL FLOAT LEVEL SETTING BS 30 60 Sport 25 32 inch BS 90STD 90D 90T 90M 25 32 inch BS 90 Sport 23 32 inch BS 175 DT 23 32 inch 4 Make adjustments in float level by bending only the brass tab which acts upon float level On dual float carburetors make certain both floats are equal before setting the float level Medium Engine Speeds Adjustment The gasoline air mixture can be adjusted by raising or lowering the jet needle at c throttle openings for medium engine speeds Standard setting is in the third groove from the top The throttle valve cutaway also affects engine operation at below c throttle opening so do not change throttle valve cutaway for only medium speeds adjustment It is recommended to raise or lower the jet needle for medium engine speeds adjustment within the range where acceleration is not adversely affected High Engine Speeds Adjustment The performance of the engine between 3 and full throttle can be adjusted by changing the main jet A higher numbered jet provides a larger orifice and conversely a smaller numbered jet provides a smaller orifice The jet number appears stamped on the side of the jet 46 OIL INJECTION SYSTEM 90cc In the conventional two stroke engine a fuel mixture of gasoli
79. ne and lubricating oil is used so that parts inside the Cranks hy engine are lubricated by oil contained in the fuel mixture In the Bridgestone Oil Injection System a premixed fuel is not necessary gasoline and oil are supplied separately to the engine Gasoline is supplied through a carburetor as in the conventional system Tm es Em A Construction and Operation The oil injection pump is installed in the transmission case The pump works as follows The worm wheel of the pump is driven through Crank shaft Drive pinion Pump Gear B The worm wheel the boss of which is cam shaped is in addition to being rotated by the pump drive shaft pushed in direction B by the plunger spring and contacts the rod c as shown in Fig 96 The worm wheel plunger slides in the direction of a or b shown by arrows in Fig 96 and 98 following the cam height 1 Oil Intake When the worm wheel contacts the rod c at the highest point of the cam the volume of the pump chamber increases and the pressure in the chamber Fig 99 decreases and releases the inlet check ball The inlet port opens and oil is sucked into the oil pump chamber i Outi chak fekt F f dIE AE i H E 1 N TM ee Le S i 2 Oil Outlet e When the worm wheel plunger slides in the direction b illustrated at Ae ball by the arrow in Fig 98 the volume of the pump chamber decreases pe 9 By decreasing the volume of pump chamber the inlet
80. ng pin is 1 14 as shown in Fig 65 Screw cable adjuster in to shorten 32 the distance out to increase the distance When properly positioned secure with cable adjuster lock nut 3 Loosen clutch adjusting screw lock nut and turn screw in clockwise until you feel it just touch the clutch throw out bearing Then turn screw out counter clockwise 1 4 turn 4 Check clutch lever for correct free play 3 8 5 8 at lever end Turn adjusting screw as required for correct free play Counter clockwise for more free play clockwise for less 5 Secure adjusting screw in correct position with lock nut NOTE The tool kit shipped with the machine contains a special socket wrench with handle which fits adjusting screw lock nut The design of this wrench enables you to hold clutch adjusting screw in correct position with a screw driver while securing the lock nut This tool incidentally also serves as a screwdriver handle in cases where heavy pressure is required See Fig 66 EARLE Apousrte ADA SEREW LOCKNYT RELEASE ARM 3 NON E ECHT atten eg cl D No further adjustment should be made on the cable adjuster unless it stretches with age Periodic clutch adjustments should be made with the clutch adjusting screw only 33 TRANSMISSION A Construction and Operation Fig 67 BS 50 60 Sport 90 cc Transmission Mechanism in Meutrol Gear Position Kick idle gear A First gear A Fourth gear A Third ge
81. nkcase section 19 Coat the abutting surfaces of the two crankcase sections with a rubber base gasket compound such as Pliobond 20 Install the 2 knock pins into the upper crankcase section and join the two sections Place all of the joining bolts into the holes provided for them and check to see that approximately L inch of thread is available between the bolt head and the crankcase before tightening any of the bolts 21 Tighten all bolts finger tight 15 Install the clutch shaft Note that the smaller ball bearing on this shaft has the one sealed side The sealed side of the bearing is to face the gears The open side faces out Note that the clutch shaft is hollow Oil is deflected by the splash shield into the cavity next to the sealed bearing It then passes through the shaft lubricating the gears on the shaft Check the shafts for freedom of rotation 16 Place the thrust washer in the kick starter ratchet gear and install the ratchet arm and pawl assembly on top of the thrust washer ee 17 Holding the kick starter gear and ratchet stopper assembly in position in the crankcase 22 Then tighten the bolts in the tightening order section install the kick starter shaft into the which is embossed on the crankcase next to crankcase Locate the splined portion of the the bolt holes The bolts with the large heads shaft into the kick starter ratchet arm so that are torqued to 120 inch pounds and the the countersunk hol
82. ns of gasoline This mixture is to be used during the first 250 miles of operation only Thereafter instruct the customer to fill the tank with regular gasoline only 3 BATTERY Fill and charge the battery 4 TRANSMISSION Fill the transmission case with 25 ounces of SAE 10W30 motor oil Transmission oil level is checked by removing the oil level plug located just in front of the kick starter shaft Do not overfill the transmission case 5 OIL PUMP GEAR BOX The Oil Injection pump is gear driven by the crankshaft and gear cavity oil level must be checked before operation e The gear cavity is located behind the oil pump and left carburetor This cavity must be kept filled with a good grade of 30 weight motor oil To fill proceed as follows A Remove left carburetor cover B Remove oil level screw This oil level screw is easily identified because it has a red fiber gasket under it C Remove the screw just to the right of the oil pump body Using a pressure type oil can fill the gear cavity through this screw hole Fill until oil appears running out of the oil level screw hole Oil level should reach lower edge of this oil level plug screw hole D Replace both screws Oil level should be checked during the first 500 miles and intermittently thereafter 6 ADJUSTMENTS A Tire Pressure 24 to 26 lbs Front 26 to 30 lbs Rear 69 Brakes check and adjust as described in owner s manual Horn check for proper operation
83. nt 4 Rotate crankshaft by putting transmission in 4th gear and S turning rear wheel until the right piston is at top dead center as _ viewed through the spark plug hole 5 Install timing screw and bar into timing hole at front of engine fig 112 This item is packed in the cycle tool kit 6 Connect one lead wire of a continuity test light to the right point condenser lead wire at the condenser with the key switch in the off position Test light is now off The other test light lead wire is grounded to engine Fig 114 57 e NOTE As you face the open end of the generator the points and condenser set on your right control the firing of the right cylinder See Figure 114 7 Rotate engine backwards by turning the rear wheel backwards until the right points close and test light is on 8 Now hold slight pressure on the timing bar and rotate the engine forward until the timing bar engages the slot in the crankshaft If the timing is correct the test light will have just gone out at this point RIGHT CYLINDER TIMING ADJUSTMENT If the test light did not go out timing is too slow or retarded or went out before engagement of timing bar timing too fast or advanced proceed as follows 1 Remove air cleaner 2 Loosen generator mounting clamp nut A fig 114 3 Slightly loosen generator positioning screw RB fig 114 4 With the timing bar inserted into the crankshaft rotate generator counter clockwise to slow
84. o DC current for charging the battery Running the machine in the daytime without the battery or fuse in place will damage the rectifier and burn out light bulbs The battery should be kept fully charged Specific gravity at approximately 70 F should read 1 260 on a fully charged battery TV 1 EW 20 0o abT 90 ce Tel Light EY JW Stop Light AN EW EV 15 7 15W Ga Banten L AN 1 5 R Siog Switth G Battery Charging 50 60 Spt Listed below are two methods of increasing the charge rate on the B S 50 60 Sport 1 Connect both the yellow wire and the white wire from the key switch to the yellow wire from the charging coil in the magneto The white wire from the magneto is left disconnected This wiring change will slightly increase the charging rate 56 2 For chronic problems caused from the cycle being driven only at very low speeds the charging coil from the B S 7 Standard can be installed to increase charging NOTE When either method is used battery water should be checked frequently and water added as necessary ELECTRICAL EQUIPMENT 175 DT The ignition system consists of contact breakers condensers ignition coil spark plugs etc Battery low voltage current is converted to high voltage current by the ignition coil High voltage current is supplied to the spark plug and when timed by the contact breakers ignites the fuel mixture in the cylinder Contact Breakers Two contact breakers are fitt
85. o the combustion chamber increasing scavenging efficiency Fig 52 Fuel intake system Fig 53 Cross section cylinder i An AN Boost port tt Transfer port j A TO d Rotary disc valve Boost port _ Tronst er port The pistons are aluminum alloy made to resist wear and yet maintain excellent mechanical property at high temperatures Pistons used in the cast iron cylinders are of high silicon aluminum alloy with a low coefficient expansion and light specific gravity Those pistons used in the aluminum cylinders are of low silicon alloy content with a lower heat expansion coefficient than the normal aluminum alloy pistons NOTE 1 Pistons for the 90 STD 90 T 90 M could be used for replacement in the 90 Sport or 175 DT but only in cases of emergency They are of a harder material and will wear the chrome faster 2 Pistons for the 90 Sport and 175 DT are not interchangeable and cannot be used in the cast iron cylinders or the 90 STD 90 T 90 M They are of a softer material and will wear rapidly against cast iron 3 The chrome plated ring used in the 90 STD 90 T 90 M cannot be used for the 90 Sport or 175 DT Chrome will not operate properly against chrome 4 Pistons made only for cast iron cylinders can be recognized by the small center drilled hole in the top of the piston 26 5 Pistons made only for chrome plated aluminum cylinders can be recognized by the small flat spot on th
86. o your left so that the guide pin is retained in the notch in the selector lever shaft 9 Install the neutral switch contact onto the end of the shift drum 20 Fig 42 10 Install the neutral switch cover over the shift drum contact This cover must be installed so that the wires from the terminals on the selector shaft switch marked 4 and D are connected to the shift drum switch cover terminals marked 4 and 5 respectively without crossing the wires 11 Placing the selector lever shaft and sprocket cover in position turn the selector lever shaft to the four speed position Connect one lead of the continuity tester to the yellow wire with green tracer running from the main neutral switch Ground the other lead Rotate the shift drum until the gears are in the neutral position and the continuity tester light goes on Place the transmission in any gear Using the selector lever move the shaft to the five speed position Rotate the shift drum until the continuity tester light comes on If you do not get a light in both the four speed and five speed neutral positions inspect the contact on the shift drum Replace if necessary 12 Install the crankshaft assembly 13 Install the oil splash shield 14 Install the transmission drive shaft locating the groove on the large ball bearing onto the bearing locating ring in the crankcase section The bushing on the other end of the shaft is located on a knock pin in the cra
87. on case 36 Remove the cotter pins from the shift forks 37 Using a screw driver tip the shift fork guide pins out of the groove in the shift drum Fig 37 38 Remove the thrust receiver mounting screws and pull the shift drum and thrust receiver out of the transmission case Hold the shift forks stationary while the shift drum is being removed Remove the shift forks from the transmission case 39 Remove the guide pins from the shift forks and inspect them for wear Notice that the guide pins are equipped with roller ends These roller ends ride in the grooves in the shift drum 19 Fig 39 40 Remove the spring clip which retains the kick starter shaft in the lower crankcase section 41 The kick starter shaft can then be withdrawn from the crankcase section Remove the ratchet assembly from the crankcase section Before reassembling the engine wash all parts in a cleaning solvent inspect for abnormal wear HI ENGINE REASSEMBLY 1 If the neutral switch was removed from the transmission selector lever shaft re install the switch assembly onto the transmission selector lever shaft Be certain that the contact is not out of round and that it is properly seated in the groove provided for it on the plastic portion of the shaft 2 Install the shaft onto which the switch assembly has been mounted into the transmission case Secure it with two Phillips head screws 3 Connect one lead of a continuit
88. onstruction and Operation ss SE ce eee ee eee eee 26 M MENA EE 63 Assembling Front Fork EE 63 CRANKSHAFT AND ROTARY DISC VALVES 27 A Construction and Operation 444444444995 ER EG GE GE 2i REAR SUSPENSION 2 0055 E SEE ESE EES RS ED ewww ews es 64 B Rotary Valve Modification 28 50 60 SPORT 90 amp 90 SPORT 0 0 ccc cee 28 FRONT WHEEL 0 0 ccc ese se es es ee ses 65 is DUAL EWE is ee EE e eee 29 Removing Front Wheel ss 0 eee eee eee eens 65 Adj sting Front Brakke ses ese ses sees SE N N N Ee oe 65 KICK STARTER MECHANISM iss seges Eg gs og lg ge ie 29 Construction and Operation N RE AE MERE EL si cence SEEESER EER TESE EERS EER SE EES EE DEE OG 66 Removing Rear Wheel 66 TN ase EE EE eee EN Adjusting Rear Brake at NENNEN NNN 67 Ps on E EE 31 B OER EE 32 PRE DELIVERY SERVICE 68 C Adjustment ene RED RS NE RR RR N EE GE EG aR RS 32 B S 90 w Oil Injection SESSE EE eee 68 TON EE 69 TRANG MIE ON ees see RR RA RO GE 34 A Construction and Operation 34 TROUBLESHOOTING ENGINE Soe SeSe 71 B Gear Shift Mechanism SS SS SS SS SS See ee 35 I PRELIMINARY CHECK ooo oeoo LLL LLL LLL al C Gear Shift Operation sesse EE RE KS ERG GE GE Ge 37 II SPARK DLG 71 ER EE 41 II ENGINE OVERHEATING 0 cece ewes T4 GABELRE TOR soas SO DS ee 42 TROUBLESHOOTING TRANSMISSION 75 A Construction and Operation 42 LMISGEDOGEARS aane
89. otate them slightly to mesh all gears and properly position the shafts 7 Install the two remaining spacers one on the end of the countershaft and the other on the end of the kick starter shaft 8 Be certain that the crankshaft end play shims are positioned on both sides of the crankshaft balance and install the crankshaft See figure 16 If a new crankshaft has been installed it will be necessary to put the crankcase gasket into position install the other crankcase section and insert several of the crankcase retaining screws tightly The crankshaft should now be checked for end play If there is more than 010 to 015 of end play additional shims must be added to the crankshaft 9 Install a new crankcase gasket locating it on the steel positioning pins Install the second crankcase section Again check transmission shaft rotation to be certain that the shafts turn freely If found to be ok reinstall the crankcase retaining screws and tighten them securely 10 Trim the excess portion of the crankcase gasket flush with the cylinder seat 11 Install the spacer on the shift arm shaft and position the shift arm shaft assembly into the crankcase Fig 17 12 Insert the shift arm pawl into the shift drum assembly Install the thrust receiver and bend the tabs on the tab washer against the flats of the bolts when the mounting bolts have been secured This tab washer prevents the bolts from loosening during engine op
90. ould be snug but rotate easily Replace the pin and bushing if necessary Oil the bushing thoroughly before installing the piston pin and piston 34 Install the piston pin and piston When installing the piston the letters EX are to face the exhaust port front on the cylinder It is important to position the piston this way since the piston pin hole is slightly off center for improved performance If the piston is installed backwards a loud knocking sound will be heard at low speeds Fig 23 Busse 2 Fig 23 L a 35 Install the piston pin retaining clips 36 Check to see that the piston rings are properly installed The chrome plated ring is the upper ring and the cast iron ring is the lower ring The rings are to be positioned on the piston so 14 that the locating pin on the piston is located in the ring gap Fig 24 The notch in the ring gap should face up If the notch faces down the rings cannot be compressed enough to permit installation of the cylinder 37 Install the cylinder onto the mounting studs and install the lockwashers and nuts securely 38 Install the cylinder head gasket and cylinder head Four flat washers are used under the cylinder head nuts Tighten the head nuts progressively and evenly to 125 inch lbs of torque The engine is now completely reassembled and ready for remounting in the cycle frame The engine mounting procedure is to be done in the reverse order of the dism
91. ounting procedure BRIDGESTONE 175 DT ENGINE DISASSEMBLY AND REASSEMBLY I Removing Engine From Frame 1 Drain transmission oil into a suitably large container 2 Raise the right hand rubber carburetor cap 3 Remove the air cleaner duct from the carburetor cap 4 Remove the carburetor cover from the right hand side of the engine 5 Remove the rubber plug from the front of the carburetor enclosure and loosen the carburetor retaining bolt 6 Remove the right hand carburetor It can be allowed to hang suspended from the throttle cable 7 Loosen the clutch adjusting screw lock nut and remove the clutch adjusting screw 8 Remove the clutch release arm and disconnect it from the clutch cable 9 Unscrew the clutch cable adjusting screw all the way out of the engine AS a 10 Remove the kick starter lever 11 Remove the cover plate on which the transmission selector lever is mounted 12 Remove the gear shift pedal 13 Raise the carburetor rubber cap from the top of the left carburetor enclosure 14 Remove the air cleaner duct from the rubber carburetor cap 15 Remove the left carburetor cover ee L 16 Remove the left carburetor 17 Remove the control cable from the oil injection pump control arm by prying the cable attaching bracket open with a screw driver 18 Remove the throttle cable adjusting screw out from the transmission cover 19 Remove the main oil pump supply line
92. placement of one cylinder and combustion chamber volume The formula can be expressed as Compression ratio Piston displacement Combustion chamber vol Combustion chamber volume 84 Example An engine has a piston displacement of 244 6 cubic centimeters and a combustion chamber volume of 41 5 cubic centimeters What is its compression ratio 244 6138 9 282 8 7 4 to 1 rounded off Compression ratio 38 2 38 2 HORSEPOWER AND TORQUE There is sometimes confusion about horsepower and torque Horsepower is a measure of how much work can be done in a given length of time One horsepower is equal to the work done when a weight of 550 pounds is lifted one foot in one second or 33 000 pounds lifted one foot in one minute Torque is merely twisting force developed by an engine and is not indicative of how much work can be done unless engine speed is known The relationship between horsepower torque and engine speed can be expressed as rpm x Torque Horsepower 5 252 Example 1 A motorcycle engine develops 30 foot pounds at 6 000 RPM How much horsepower does it produce at that speed 6 000 x 30 180 000 34 3 foot pounds rounded off 5 202 5 252 It is sometimes desired to know how much torque is developed by an engine when horsepower and rpm are known The formula can then be written as Horsepower x 5 252 Torque rpm Example 2 During a dynamometer test an engine developed 14 7 horsepower at 3 500 rpm How mu
93. rail 11 Banking Angle 12 Net Weight 13 Fuel Tank Capacity 14 Front Brake 15 Rear Brake Electrical Equipment 1 Head light 2 Tail light 3 Stop light 4 Turn signal light 5 Battery Manual Multiple discs in oil bath 4 speed constant mesh gear amp foot control Primary Helical Gear 1 8 95 Ist 122 77 2nd 1 1 72 3rd 1 1 23 Ath 1 0 924 Secondary Chain 1 2 438 Total Gear Ratio Ist 1 26 58 2nd 1 16 51 3rd 1 11 81 Ath 1 8 86 1 830 mm 72 0 inch with Standard Handle Bar 660 mm 26 0 inch with Flat Bar 580 mm 22 8 inch 970 mm 38 1 inch 750 mm 29 5 inch 30 1 inch 90 Spt 1 160 mm 45 7 inch 150 mm 5 9 inch 2 50 17 4 ply 2 50 17 4 ply 1 6kg cm 22 8 lbs in Same 90 Spt 2 4 kg cm 34 2 lbs in 28 4 Ibs in 90 Spt 63 degrees 80 mm 3 15 inch 45 degrees 47 degrees 90 Spt 79kg 1741bs 7 0 L 1 85 US gal 2 25 US gal 90 Spt including 0 264 gal reserve 0 396 gal 90 Spt Right Hand Right Foot 6V 15 15W 6V 2W 6V 8W 6V 8W 6V 4AH Engine 1 Type 2 Piston Displacement 3 Bore amp Stroke 4 Compression Ratio 5 Max Brake Horsepower 6 Max Torque 7 Air Intake System 8 Starting System 9 Charging System 10 Ignition System 11 Ignition Timing 12 Spark Plugs 13 Carburetors 14 Engine Lubrication 15 Fuel 16 Transmission oil Performance 1 Max
94. rectifier by using the red post and touching the yellow blue and white and proceed as above e If no positive conclusion can be made from this test substitute another rectifier and test as in 2 7 If the charge reading is still below the 3 5 amp with the high low charge switch in the on position and operating the high low charge switch from on to off does not change the charge rate at half to full throttle suspect a faulty switch and connect the brown wire from the generator to the white post of the rectifier if charging is then correct replace the charge switch 8 Generator Test The generator Can be checked with a test light A battery operated test light should burn when connected to any two of the yellow blue or brown wires The test light should not light from any wire yellow blue or brown when the other test lead wire is grounded to the generator frame 9 It all components seem to test satisfactory and charging is still below standard the generator magnets may be weak and replacement would be necessary 10 When checking the charging system always check the terminals on the wires ends to make sure they have good contact 11 For the proper readings always use a charged battery when testing 12 If the charge rate is found satisfactory and battery becomes discharged the battery may be defective and will not hold a charge Check the battery after fully charging it and if the specific gravity of the fluid is not above
95. ren erena 75 B Functions of Various Darts 44 me C Adjustment 6 65 555545 66seKeeeeoe see NENNEN CNN 45 TROUBLESHOOTING ELECTRICAL ccccceeee 76 TO ADJUST FLOAT LEVEL ese se ese se see se se see se 46 50 60 Spt Oe 76 PRM WEE H oos dode sd de de de N IG 76 OIL INJECTION SYSTEM 90e EE nen seen ese 47 Il CHARGING SYSTEM SG 76 A Construction and Operation 47 Ill BRAKE LIGHT SWITCH cc LLL LLL 76 B Adj stment EE 48 IV HEAD LIGHT ccc cece cee enee 71 C Special Attention to the Oil Injection System 49 V HORN GIROLT 77 VI SELENIUM RECTIFIER osse ss so sesse ss ses TI OIL INJECTION SYSTEM 175DT sessie egg egg ig 50 VODE ko EET EER EE EE EE DE OD ETIKET EL EE U7 A Construction and Operation see EE EE EE ee ee 50 AU MODELS ET 78 BATSMEN ooie aoe DR EE ee a a aad andes 51 C Special Attention Pump Modification 52 INSPECTION AND MAINTENANCE ccccecee 79 ELECTRICAL EQUIPMENT 50 60 Sport 90cc 93 SERVICE STANDARDS eie ee ee ee eee ee ee ences 80 A Ignition System 58 e Contact Breaker EE 53 APPENDIX 0 c cece cece ccc eceeceueeeeuteueunennes 81 lenition Eelere 53 USEFUL FORMULAS AND TABLES 81 TO SET TIMING ees se se see se se see ke Ne see Ne 53 CONVEROIONS Se aa urrera nnn 82 Condenser 54 EXAMPLES OF CONVERSIONS LLL LLL LLL LLL 83 Spark da
96. rent to DC to trickle charge the battery The battery is a 6 volt 4ampere hour battery furnishing current to the brake light and the neutral gear indicator light The battery also functions as a stabilizer in the electrical circuit At high speeds the magneto puts out from 12 to 18 volts This current passes through the battery which stabilizes it at 6 volts It is important that the battery is fully charged at all times since a discharged battery will not offer sufficient resistance in the electrical circuit When battery charge is low the headlight and taillight bulbs will be burned out instantly when they are turned on 55 E Testing the Lighting Coil Silicon rectifier The efficiency of the lighting coil can be checked by connecting an ammeter of approximately 2 ampere reading capacity in series with the battery fuse as indicated in the drawing below Start the engine and measure the current at approximately 2 500 rpm s and approximately 8 000 rpm s With the key switch in the ignition only position at 2 500 rpm the current should measure 0 1 amp Voltage should register more than 6 volts At 8 000 rpm s the voltage should register less than 9 volts Ifthe measurements are Pe 7 within plus or minus 10 to 20 per cent of the standard rate indicated the coil is satisfactory If it is above or below these tolerances the lighting coil should be replaced F Selenium Rectifier The selenium rectifier transforms AC magneto int
97. ring Kick starter geor C Fig 64 SN The clutch on all Bridgestone rotary disc models is a multiple disc type running in oil The clutch is mounted on the transmission countershaft Clutch friction fiber plates are fitted inside the clutch housing with six teeth so that they turn with the clutch housing and driven gear Clutch friction plates and inner plates are fitted alternately steel plate first then fibre plate etc with the inner steel plates fitted to the clutch hub with teeth 50 60 Spt Clutch Friction Plate 3 Inner Plate 3 Clutch Springs 6 Fitting Tension 110 inch lbs 90 ce Clutch Friction Plate 5 Inner Plate 5 Clutch Springs 6 Fitting Tension 120 inch lbs 175 DT Clutch Friction Plate 6 Inner Plate 5 Clutch Springs 6 Fitting Tension 130 inch lbs B Operation Located between the engine and transmission the clutch transmits or cuts off engine power to the transmission and rear wheel Engine power is transmitted from the pinion gear on the crankshaft through the driven gear on the clutch housing The clutch hub friction plates and inner plates all fit inside the clutch housing When pressed together by the clutch springs the plates come into solid contact and rotate as a unit The clutch hub is spline fitted to the transmission countershaft which turns the transmission gears When the clutch lever is pulled the clut
98. ring into the union bolt Then with the oil line connector and picking washers installed on the bolt screw the bolt into the outlet port hole 4 The style of oil pump can be determined by viewing into the outlet port holes The outlets on the old style pumps have no ball valve seats machined in them and the check Brass Check l Val e ball will pass through the outlet into the oil pump body Pd onngctors e The new style pumps have check ball valve seats machined in the outlet ports 5 New style oil pump assemblies are interchangeable with the old style assembly An additional change was made in Feb 1966 Serial No 16B This change incorporates the ball and spring check valves into a new style outlet connector The ball and spring are assembled inside of the new connector and eliminate the possibility of incorrect assembly or loss of these parts 52 The new connectors are easily identified because they are made of brass instead of aluminum These new connectors are interchangeable on any of the old type pumps When they are installed on old type pumps the ball and spring must be eliminated from the connecting bolts Any old type pump can be converted to the latest style by installing 2 of these new outlet connectors The old type union connector has been abolished A simple check of the oil injection system can prevent serious damage when the machine is operated Dirty or plugged oil lines tanks or filter could prevent
99. rly molded into the valve disc The valve now fits onto a separate splined collar Old style valves can be replaced by the new style valves by also installing the new splined collar and a new shorter crankshaft drive pin Cylinder Transfer port FOR 50 60 SPORT 90 amp 90 SPORT Because of the new 2 piece design valve timing must be aligned when installing a new style valve The collar has a slot that is easily aligned on the pin in the crankshaft The rotary valve must be installed on the collar with the dot mark on the valve aligned with the dot mark on the collar Fig 59 28 Fig 39 COLLAR MARK VALVE MAAK SINGLE CYLINGER YALVE FOR THE 175 DUAL TWIN The rotary valve used on the 175 Dual Twin is interchangeable for either left or right side and must be timed accordingly when installed The valves are marked with an L and R The appropriate mark is aligned with the key slot in the crankshaft collar depending on whether the valve is being used on the Left or Right side of the engine get ur ALIGN L WITH KEYSLOT FOR LEFT SIDE CC Li ALIGN RE WITH KEYSLOT FOR RIGHT SIDE 175 ROTARY VALVE KICK STARTER MECHANISM Construction and Operation All Bridgestone rotary valve models are equipped with the primary kick starting system In this method the engine can be started in any gear by simply squeezing the clutch This is possible because this system employs an extra set of gears for by passing th
100. ry to bring the battery to a fully charged condition SP GR CHARGE D 1 260 100 1 220 75 1 160 50 1 105 25 CHG REQ IN AMP HRS 0 18 A H 30 A H 45 A H e While it is theoretically possible rarely if ever will a dry charged battery be found to be fully charged when the electrolyte is added 5 To charge the filled battery a 24 A H charge rate may be used in the initial state of charging The charge is then completed with a amp trickle charge The approximate charging time for each of these two charge rates is indicated in Table 2 This table is based on the hydrometer reading taken in 4 above one ARCHA euan 2 5 A H CHG 1 240 2 Hrs plus 10 Hrs 1 220 4 Hrs plus 20 Hrs 1 160 8 Hrs plus 20 Hrs 1 105 10 Hrs plus 30 Hrs e NOTE If battery case becomes hotter than 115 warm to the touch charge rate must be reduced immediately Overheating will cause severe battery damage e Asa matter of practice the maximum charge rate depends largely on the air temperature of the area where the battery is being charged A charge rate of up to 50 of the total charge required see Table 1 can be used IF TEMPERATURE OF THE BATTERY CASE DOES NOT RISE ABOVE THE POINT AT WHICH IT IS JUST WARM TO THE TOUCH 115 F Therefore the cooler the surrounding air temperature the higher the allowable charge rate CAUTION 1 DO NOT OVERCHARGE Take specific gravity readings frequently during charging period 2 CONNECT CHARGE
101. s mixture a correct rich mixture for starting a cold engine is inhaled into the engine through the nozzle located behind the main bore NOTE It is most important that the throttle valve be left closed when starting the engine If it is not the rich gasoline air mixture will be leaned out Too the raising of the throttle valve hampers the inhalation of this correct mixture by taking away the vacuum ordinarily created when the kick starter is depressed 2 Slow channel mainly for idling The suction stroke of the piston induces air at the pilot outlet of the carburetor so that gasoline is metered through the pilot jet and air is drawn through the pilot air hole and metered by the air adjusting screw The gasoline and air make a rich fuel mixture which jets from the pilot outlet into the main bore where it mixes with a small amount of air and is supplied to the engine along with a correct amount of oil injected into the intake between the carburetor and the engine 3 Main Channel mainly for medium and high speeds Air entering the carburetor from the air cleaner passes under the throttle valve and is inhaled into the engine as the main air flow Induction is created at the needle jet by this main air flow and gasoline in the float chamber is metered by the main jet and enters the needle jet This gasoline passes through the gap between the needle jet and jet needle and flows into the main bore of the carburetor The gap between the needle jet
102. s on the clutch the machine travels gear These marks are located between gear teeth approximately three inches apart 31 Install the clutch onto the transmission countershaft NOTE On newer models fit the thrust spring over the clutch drive gear install the clutch assembly except for the hub replace the splined washer and then install the clutch hub 32 Secure the clutch with the bend washer and hex nut The clutch stopper is installed to prevent the clutch from rotating during tightening of this nut 33 The edges of the washer are bent up against 33 The edges of the washer are bent up against the flats of the nut to prevent its loosening the flats of the nut to prevent its loosening during operation during operation 34 Install the six clutch springs and install the 34 Install the six clutch springs and install the clutch thrust plate Be certain that the ball clutch thrust plate Be certain that the ball bearing on the thrust plate faces out bearing on the thrust plate faces out 35 Install the pinion gear onto the crankshaft 35 Install the pinion gear onto the crankshaft e ALIGN THE MARKED TOOTH ON THE e ALIGN THE MARKED TOOTH ON THE GEAR WITH THE PUNCH MARK ON ONE GEAR WITH THE PUNCH MARK ON ONE OF THE CRANKSHAFT SPLINES OF THE CRANKSHAFT SPLINES e THIS MARKED TOOTH MUST ALSO BE ALIGNED WITH THE LOWER OF TWO 27 Install the small O ring which seals the oil PUNCH MARKS ON THE CLUTCH passage for the oil injec
103. screw D clockwise a slight amount Never adjust more than c turn at a time until the cycle is operated and again check C Special Attention to the Oil Injection System The following procedures are necessary after filling up the oil tank before break in or after disassembling oil tank or pump 1 Remove the carburetor cover by screwing out the 4 carburetor cover screws 2 The oil inlet tube black and the oil tube transparent which are connected to the oil pump are shown in Fig 109 3 The oil outlet tube transparent is connected to the rotary valve cover e Procedures 4 and 5 are necessary to exhaust any air bubbles from the rotary valve cover and obtain free flow of oil from the pump to the outlet tube 4 Loosen the oil inlet union bolt one or two turns do not take out this bolt and pump oil out from the union bolt on oil tube black connecting oil tank and oil pump by pinching the oil tube alternately with fingers of both hands as shown in Fig 109 A9 e NOTE Pinch part A first then pinch part B repeat alternately until air bubbles are eliminated and the oil flows freely out of the union bolt 5 Tighten the oil inlet union bolt and repeat pinching with fingers check the oil flow in the outlet tube transparent to the inlet in the rotary valve cover e If there is no oil flow in the outlet tube transparent repeat procedure 4 A simple check of the oil injection system can prevent serious
104. screws are not installed at this time because they also secure the oil pump gear case 49 Using a new gasket install the oil pump and oil pump gear case assembly onto the left rotary valve cover locating the gear box by means of the two pins in the rotary valve cover 50 Install the four screws which secure the gear box to the rotary valve cover 51 Install the screw on the left side of the oil pump which secures the oil pump to the gear box 52 Remove the oil pump gear box oil level screw This screw can be identified by the red fiber washer beneath it 53 Using a pressure type oil can inject oil through the screw hole on the right side of the oil injection pump until oil is seen coming out of the oil level screw hole NOTE The oil pump gear cavity on those models after serial No 16G 11761 is lubricated automatically from the transmission 54 Replace the oil level screw and fiber washer and install the right hand oil pump attaching screw Tighten securely ML oe EVER wd 55 Using the pressure type oil can fill the right hand oil injection line before installing a line onto the right banjo connector When tightening the banjo connector union bolts use caution so as not to overtighten the bolts These bolts are hollow and can be broken Note that a washer is used on either side of all banjo connectors 56 Install the left oil line onto the oil pump and onto the left rotary valve cover 57 Install the
105. sion in neutral to check for brake a a drag Fig 138 1 Chain adjustment is correct when chain slack is approximately d inch up or down 2 To adjust loosen rear axle nut and adjust with the chain and adjusters on the ends of the axle turning them back or forward an equal amount to keep correct alignment of chain wheels ei Me fe S Es S adjusting nul ep OR As Fig 139 67 PRE DELIVERY SERVICE After the cycle has been uncrated and assembled the following service and adjustments must be made to insure proper functioning of the machine B S 90 w Oil Injection 1 OIL INJECTION Fill the oil supply tank with a good grade of 2 cycle oil for best results use Rockford oil Caution The oil tank must never be allowed to run dry Remove the right carburetor side cover and loosen but do not remove the oil supply line at the pump the supply line is the rubber line connected at the lower edge IE of the pump With this fitting loosened and the oil tank filled with oil oil should flow freely from the fitting If it does not it may be necessary to run your finger along eat the oil line while squeezing the line to remove trapped air When oil will flow freely from this fitting retighten the connector bolt but do not overtighten The injector pump has a separate gear box and oil filler screw The gear box oil level should be checked and corrected as necessary Remove the plug and fill with a pressure type o
106. supply when the throttle is more than threequarters open but at smaller throttle openings although the fuel passes through the main jet the amount is diminished by the tapered needle jet Listed below are the carburetor main jet sizes that are used as standard equipment on the Bridgestone rotary valve models Also listed are other sizes that are available ORIGINAL EQUIPMENT AVAILABLE MODEL Main jet number 15mm Carburetor 110 100 56 60 Sport 100 90 before 12N 130 90 12N and after 120 90 Trail 130 90 Mountain 130 17mm Carburetor Set of 5 110 150 90 Sp before 14L 90 Sp 14L and after Set of 5 110 150 175DT Set of 5 110 150 2 Air Jet 44 The air jet controls the flow of air entering the needle jet The fuel passing through the needle jet mixes with the air coming in from the air jet Needle Jet 3 Needle Jet At full throttle or at medium speeds the fuel is first regulated by he main jet and the needle jet acting simultaneously 4 Jet Needle Fig 90 The tapered jet needle attached to the throttle valve works in the needle jet and adjusts the air fuel ratio at medium 4 to 34 throttle openings Jet Needle 5 Throttle Valve Throttle Valve gt i The throttle valve is cut away on the 4 inlet side and controls the flow of main fuel supply from c to 3 4 throttle opening The extent of cut away is 12 marked on the valve viz 2 0 for lt 2 0m m cut away EI
107. t 45 Unhook the lower end of the kick starter return spring from the crankcase and lift off the spring 46 Using the circlip expander special tool remove the circlip from the kick starter shaft 47 Using an open end wrench remove the shift drum stopper pivot screw Fig 12 Unhook the shift drum stopper spring and remove the shift drum stopper Inspect it for bends of abnormal wear The disc on the end of the shift drum stopper should rotate freely 10 r Re 4 i A Piwal verde a K e 48 Lift the shift arm pawl free of the shift drum and holding it in this position carefully withdraw the shift arm and shaft assembly Inspect the shift arm assembly for bends damage or abnormal wear Remove the thrust receiver 49 Position the engine on the bench with the magneto side facing upwards and remove the crankcase retaining screws It may be necessary to use an impact driver to remove these screws as they are inserted very tightly The impact driver will enable you to remove the screws without damaging the screw heads See tool list figure 1 The drive sprocket should be removed as soon as the engine is turned magneto side up 50 With all crankcase retaining screws removed carefully tap the crankcase with a soft faced hammer to break the gasket seal and separate the crankcase halves 51 Carefully lift out the two transmission shafts and gears together with the shift drum shift fork assembly 52
108. tarting System 9 Charging System 10 Ignition System 11 Ignition Timing 12 Spark Plug 13 Carburetor 14 Fuel Mixture 15 Transmission Oil Performance 1 Max Speed 2 Climbing Gradient 3 Fuel Consumption 4 Min Turning Radius 5 Acceleration 6 Braking Distance Frame Suspension 1 Frame Type 2 Front Suspension 3 Rear Suspension SPECIFICATIONS 90 cc 2 stroke Single Cylinder 88 c c 5 39 cu inch 50 mm x 45 mm 1 97 x 1 77 inch 6 8 1 7 8 HP 7000 rpm 8 8 HP 8000 90 Spt 0 85 kg m 5000 rpm Rotary disc valve Kick Starter A C Magneto Flywheel Magneto 21 degrees before T D C N G K B 7H AMAL Type VM 15SC VM 17SC 90 Spt Gasoline 0 6 litre 0 158 US gal in transmission SAE 30 summer SAE 20 winter SAE 10W30 in all seasons 95km h 60mph 105 kh h 65 mph 90 Spt 1in3 75 km L 177 mpg 20 mph at 30 km h on paved flat test road 1 8 m 70 8 inch 13 0 seconds 0 200 m 12 0Sec 90 Spt 6m at 35 km h 20 feet at 22 mph Pressed Steel Backbone Type Telescopic Fork with Hydraulic Damper Swinging Arm with Hydraulic Damper eTransmission 1 Clutch 2 Transmission 3 Gear Ratio Dimensions amp Weight 1 Overall Length 2 Overall Width 3 Overall Height 4 Saddle Height 5 Wheel base 6 Road Clearance 7 Tire Size Front Rear 8 Tire Pressure Front Rear 9 Caster 10 T
109. tch stopper a special tool in place to hold the clutch stationary while the clutch retaining nut is removed 16 Loosen but do not remove the generator gear mounting bolt 17 Remove the clutch as a unit by placing the fingers of both hands around the clutch gear while holding the center of the clutch in position with your thumbs On more recent models of the 173 DT a thrust spring fits over the drive gear of the clutch On these models remove the retaining nut the clutch hub the splined washer the remaining clutch assembly and then the thrust spring in that order 18 Insert the aluminum piston seat under the upper end of one connecting rod to hold the crankshaft stationary and loosen the pinion gear retaining nut THIS IS A LEFT HAND THREAD Remove the retaining nut and the gear from the shaft Remove the right rotary valve cover 20 Remove the right rotary valve and collar It is not necessary to remove the spline from the crankshaft 21 Mount the flywheel puller in the threaded holes provided in the generator gear and with the center bolt of the special tool bearing against the generator gear bolt remove the generator gear from the tapered generator shaft e B S 173 models after serial No 16G 11761are equipped with a timing idle gear also This gear is removed at this time 22 Remove the drum stopper retaining bolt and drum stopper Do not lose the spacer washer beneath the drum stopp
110. tion chamber Plate gasket ae and result in cylinder damage Gasket y or oh Side electrade m i Point gap B Testing the Ignition Coil Bi T 6 6 0 mm The ignition coil can be tested efficiently by connecting the spark plug cap to one lead of a gap tester Ground the other lead of the tester and kick the kick starter A spark should jump the quarter inch 4 gap If the spark does not jump this gap suspect that the ignition coil is defective Points condenser and timing should be checked however before replacing the ignition coil C Technical Standards The technical standards of electrical components are indicated below MODELS DESCRIPTION SPECIFICATIONS 50 60 Spt 90cc Condenser Capacity in Microfarads 0 25 to 0 30 mfd x x Ignition Coil Operating Voltage 0 5 volt X X Primary Operating Amperage 1 5 to 2 5 amps A A Ignition Coil Primary Continuity 1 5 to 2 0 ohms X X Secondary Continuity 8000 to 9000 X X ohms Lighting Coil Continuity Yellow wire to ground 0 2 ohms X 0 5 ohms X Continuity White wire to ground 0 1 ohms X 0 5 ohms X NOTE Refer to Troubleshooting section for proper testing procedures in checking generator and charging system on B S 175 DT D Lighting System The magneto armature plate also contains a lighting coil Fig 111 The lighting coil provides current to the headlight and taillight It also provides AC current to the selenium rectifier which converts this cur
111. tionary mark See Fig 113 e CAUTION adjustments must be made if ignition occurs before the flywheel mark reaches the magneto case mark In this case timing is too far advanced 6 To adjust timing measure point gap at its widest open position The timing marks will not be 2 DEGREES aligned when this gap is 3732 INCH measured MAKIMUM a To retard spark close the point si gap by 001 at a time until the f light dims when the flywheel CRANKCASE MARK mark is 3 32 below the magneto case mark Secure the point adjusting screw and recheck FLYWHEEL MARK b To advance spark open the point gap 001 at a time until pene tine the tester light dims when the marks are aligned as in Fig 113 e NOTE It should be possible to time the engine by point adjustment alone if the magneto armature plate has not been moved from its factory setting The contact point gap can be anywhere between 012 to 016 e Ifthe engine cannot be timed with the resulting point gap within this range loosen the three armature plate screws and move the plate slightly in the direction you want the flywheel mark to move for proper alignment as shown in Fig 113 Then proceed to make fine timing adjustments as set forth above Condenser Fig 111 The condenser is mounted on the armature plate and its function is to absorb the current generated when the contact breaker points open It also assists the functioning of the ignition coil Always chec
112. tor to the right carburetor adapter e Install the spring washer and hex nut This is a left hand thread 28 Install the crankshaft collar 29 Install the right rotary valve cover Before installing check to be certain that the 100mm O ring is in good condition and in place in the groove provided for it in the rotary valve cover Also check the condition of the center oil seal The rotary valve cover is installed by aligning the pin Ee a e j 36 Put the piston seat in place under the connecting rod upper end and tighten the pinion gear nut securely 37 Turn the engine around so that you face its left side Fig 47 22 38 Install the generator strap and mount the generator Do not tighten the generator mounting bolts securely 39 Again facing the right hand side install the generator gear so that the marked tooth on this red fiber gear is aligned with this upper most of the two marks on the clutch gear Be certain that the generator gear is on the woodruff key in the generator shaft NOTE THE POSITION OF THE PINION GEAR CLUTCH GEAR AND GENERATOR GEAR AS REFERENCED BY THE MARKED TEETH IS ESSENTIAL IF THESE GEARS ARE NOT PROPERLY ALIGNED AND THE PINION GEAR IS NOT PROPERLY POSITIONED ON THE MARKED SPLINE OF THE CRANKSHAFT IGNITION TIMING WILL BE IMPOSSIBLE e NOTE The timing idle gear on those models after serial No 16G 11761 is installed just prior to the generator gear WITH THE PINION GEAR ALIGNED
113. um Pawl The shift drum pawl is attached to the shift arm and serves to rotate the shift drum by means of pulling or pushing action on the shift pins attached to the end of the shift drum 3 Drum Stopper The shift drum stopper holds the shift drum in position between gear shift operations by lodging between the drum shift pins 4 Gearshift shaft The gear shift shaft serves to connect the shift arm and shift pawl to the footoperated gearshift lever 5 Gearshift Lever 39 The gearshift lever is located on the left side of the cycle and is foot operated Each time the front of the lever is depressed or lifted the transmission is shifted either one gear up or down respectively Pedal pushed down front with foot once showing drum advanced one notch engaging 1st gear 2 3 Ah and Neutral follow in succession Back pedal tread pushed down with foot once showing drum turned in the opposite direction and shifting gear in reverse Ay 36 C Gear Shift Operation The rotary valve engines are equipped with rotary type shift mechanisms Each time the shift pedal is depressed with the toe the transmission shifts one gear higher Starting in neutral if the pedal were depressed and released 3 times the transmission would shift from 1st to 2nd to 3rd to 4th and back to neutral Fig 71 Depressing the rear portion of the pedal with the heel shifts the transmission down one gear lower each time it is depressed Gear Sh
114. ure of the complaint As a general rule in following this systematic procedure you will be able to locate the cause and make a prompt and inexpensive correction Outlined here and on the following pages are recommended procedures to follow in systematically searching for whatever problem s might exist I PRELIMINARY CHECK When the cycle does not accelerate or attain rated top speed check TIRES Properly inflated BRAKES Dragging AIR CLEANER Dirty MUFFLER Carbonized TRANSMISSION Overfilled CHAIN Too tight Dry FUEL COCK On Plugged FUEL TANK VENT Plugged Deficiencies in any of these areas will seriously affect performance II SPARK PLUG Its appearance if it has been run for any time in the engine will put it into one of three categories It will be normal Insulator light brown or gray Slight electrode wear It will be burned Burned or blistered insulator Fig 148 71 It will be fouled Fig 147 A PLUG APPEARS NORMAL A Oil Fouled Wet oil deposits Minor electrode wear B Deposit Fouling Red yellow brown and white deposits indicate use of incorrect oil or high test gas Check spark with gap tester Electrodes should be spaced La apart Good spark will easily jump this gap WEAK SPARK Spark jumps plug gap but not tester gap 1 POINTS a Worn b Incorrectly gapped c Burned d Dirty 2 CONDENSER a Defective
115. y As the dynamo mounted on this motorcycle is a six pole type AC Dynamo with large output a selenium rectifier with a large area is used The three phase bridge all wave rectifying system is used so that charging performance is excellent As show in the illustration the charging current flows in the direction indicated by a solid arrow during half a cycle and in the next half cycle flows in the direction indicated by a broken arrow Charging current always flows in the same direction and the AC current is rectified most effectively Coil Care must be taken to prevent high temperatures in the rectifier wetting with water and handling No trouble from high temperatures will be experienced if the rectifier is mounted in a properly ventilated position Take care not to wet the rectifier when washing the motorcycle If the dynamo operates Fig 122 Selenium with the secondary circuit DC side of the rectifier disconnected and voltage rises too high sparks will be generated in the synthetic materials in the layers of the selenium rectifier Spots where sparks are generated will be burned and electrical Basic plate current will flow in the reverse direction through the burned parts so that electrical current from the battery will flow to the ignition coil when the engine stops This will decrease the magnetic power of the generator Take care not to run the engine with the selenium rectifier disconnected yo vopn Fig 1
116. y tester to one of the leads from the switch cover and ground the other continuity tester lead Rotate the selector lever shaft until the continuity tester lights Connect the lead of the continuity to the other switch case lead and with the other continuity tester lead grounded again rotate the shaft until the continuity tester bulb lights If the bulb will not light in both positions check the installation of the switch contact and if it is out of round replace it 4 Place the fifth speed shift fork into the transmission case so that the guide pin boss faces the transmission selector lever shaft NOTE For installation of the modified shift fork which appears on models after serial No 16B 04739 see page 38 under TRANSMISSION 3 Fit the two main shift forks which are identical and interchangeable together and place them in the transmission case 6 Place the thrust receiver in position in the end of the shift drum and insert the shift drum through the transmission case and through all three shift forks Secure the thrust receiver with the two mounting screws and star washers Fig 41 7 The guide pins are inserted into the main shift forks so that the roller ends are positioned in the shift drum groove Install the cotter pins in the shift forks so that the cotter pins may be spread around the curved part of the guide pin bosses 8 Install the fifth speed guide pin spring and guide tipping the shift fork t

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