Owners / Service Manual
Contents
1. Figure 7 Trained technicians with precision gauging and proper assembly fixtures carefully assemble all Cobra engines to specific clearances If you feel you have the skills and the appropriate tools to perform the following service tasks please follow the instructions closely The part numbers are listed throughout to help you when ordering parts from your local Cobra dealer If you don t feel comfortable with the service work simply take your engine out of the frame and sent it to Cobra Precision Engines 11511 Springfield Road North Lima Ohio 44452 Cobra has specialized mechanics that will go through the entire engine replacing gaskets bolts any old part that is worn The engine will be rebuilt using the same precision gauging and assembly fixtures as when it was assembled new Before leaving the engines performance will be measured on a dynamometer to ensure that your engine is operating at its highest potential All this for one low nominal fee Call 830 549 9603 for details ES1 Engine Service One method for determining whether the top end of your engine needs rebuilt is to perform a WOT Wide Open Throttle kicking compression test Before performing the procedure please read the caution notes below CAUTION e There appears to be a wide range of variability in reading compression gauges across the country e The head volume of this Cobra Motorcycle is very small and so requires many ki2. 16 Front Brake Adjustment sss 14 Front Forks Parts EIS 46 DEVIC ees 46 Fuel System Parts 38 38 General 10 Ignition 32 33 Jetting HOw TO 39 SOCK 4 Lubrication Recommended 4 Maintenance Schedule 11 TDS 11 Oil Recommended 4 Optional Components 7 Parts List 38 ee en ae pee 29 Cute ee re 30 e erecta eee 17 Front Forks 46 Rear Sho0k ass ate dehet 44 43 Rear Brake 14 Rear Shock 45 Rear Wheel 42 PllBES 2 43 FOCUS dica rece t E et 41 Rotor TOQUE 6 Shock herbaria 45 Spark Plug Recommended 4 4 torque 6 Stating 9 Stator TORQUES cathe 6 re 10 19 Transmission Specifications 4 Transmission Lubricant Replacing
3. 35 4 8 Remove ignition cover using a 9 64 hex key four places 9 Remove belt retainer screw using a 1 8 hex key Figure 24 item 1 10 Remove belt retainer water pump belt and water pump fan pulley 11 Remove bearing retainer screw using a 3 32 hex key Figure 24 item 2 Figure 24 12 Heat engine case around area of impeller lightly with a small Burnsmatic propane torch Using a 3 8 diameter x 8 long steel rod tap impeller assembly out of engine as shown in figure 25 Figure 25 CAUTION Too much heat can be detrimental to the engine cases 13 The shaft assembly is serviceable Use a 1 8 hex key to remove impeller retainer screw Remove impeller seal and both bearings Check shaft for wear in the area of the seal If there is any sign of wear like a groove replace the shaft 36 Figure 26 14 Reinstall new bearings seal and impeller Clean all threads and use green wicking bearing retainer thread locker 15 Using a liberal amount of grease on the outside seal bearings and inside of case reinstall bearing assembly by using a 0 500 ID by 1 000 OD steel tube 2 long and tap on end of tube per figure 27 Figure 27 16 Re assemble in same order of disassembly Clean threads and use green wicking bearing retainer thread locker on the belt retainer screw 37 ES6 Fuel amp Air System Carburetor Tools recommended for carburetor service e S
4. tte 12 Troubleshooting 48 etie tremens 10 WARNING eene 2 49
5. 2003 CM50 Owners Service Manual CHAMPIONS START HERE For parts orders contact your local dealer To locate your closest Cobra dealer log on to www cobramotorcycle com or call 330 549 9600 If you need technical assistance contact your local dealer or call the Cobra Technical Support Hotline at 330 549 9603 Cobra Motorcycle MFG Inc 11511 Springfield Road North Lima Ohio 44452 MCCM2003 6 1 DISCLAIMER OF WARRANTY This motorcycle is sold as is with all faults obvious or not There are no warranties expressed or implied including any warranty of merchantability and warranty of fitness for any particular purpose WARNING THE COBRA CM50 IS A COMPETITION MODEL ONLY AND IS NOT MANUFACTURED FOR NOR SHOULD IT BE USED ON PUBLIC STREETS ROADS OR HIGHWAYS THE USE OF THIS BIKE SHOULD BE LIMITED TO PARTICIPATION SANCTIONED COMPETITION EVENTS UPON A CLOSED COURSE BY A SUFFICIENTLY SKILLED RIDER AND SHOULD NOT BE USED FOR GENERAL OFF ROAD RECREATIONAL RIDING IMPROPER USE OF THIS MOTORCYCLE CAN CAUSE INJURY OR DEATH THIS BIKE IS INTENDED FOR EXPERIENCED RACERS ONLY AND NOT FOR BEGINNERS IT IS YOUR RESPONSIBILITY AS THE OWNER OF THIS COBRA MOTORCYCLE OR AS THE PARENT OR LEGAL GUARDIAN OF THE OPERATOR TO KEEP THIS COBRA MOTORCYCLE IN PROPER OPERATING CONDITION THIS BIKE WAS DESIGNED FOR RIDERS THAT WEIGH LESS THAN 80 LBS WITH FULL RIDING GEAR AND SHOULD NOT BE OPERATED BY RIDER
6. brake adjustment Tools recommended for front brake maintenance e 10mm open end wrench Figure 3 from the brake lever Figure 4 from the brake hub From the brake lever 1 Loosen the locking nut on the brake lever 2 Adjust the bolt to desirable position 3 Tighten the locking nut From the brake hub 1 Loosen the 10mm nut on the hub 2 Adjust the brake cable to desirable position 3 Tighten the 10mm nut CAUTION If you tighten the front brake up too much the brakes may hang up causing the brake pads to wear incorrectly and prematurely M4 Rear brake adjustment Tools recommended for rear brake maintenance e 10mm open end wrench There are 2 adjustments on the brake Figure 6 adjust brake lever free play 14 Figure 5 adjust brake lever free height From the brake lever 4 Loosen the 10mm nut on the back of the brake pedal 5 Adjust the bolt to desirable position 6 Tighten the 10mm nut From the brake hub 1 Adjust the wing nut up to desirable position CAUTION If you tighten the wing nut up too much the brakes may hang up If so the brake pads will burn up and need replaced M5 Air Filter Cleaning Tools recommended for air filter maintenance e 2 Phillips head screwdriver e 4mm hex key Allen e Foam filter oil Procedure Removed the seat with the 4 mm hex key Remove the two Phillips head screws holding the filter to the entrance of the airbox Clean the filte
7. deposits indicating a rich mixture or improper oil type quantity can be removed with solvent b Crusty deposits indicating dirt ingestion can be removed with solvent and may require some scraping 2 Abrasions a Pitting or erosion indicates detonation and may require cylinder head replacement also i Retard the ignition timing ii Use a higher octane fuel b Missing chunks or indentations indicate broken hardware or ingested items replace the cylinder head 4 Remove the cylinder INSPECTION NOTE Inspect the cylinder bore for abrasions deposits and missing coating 1 If abrasions scrapes scratches pitting etc are found replace the cylinder 2 If deposits are all are found a Clean with muratic acid b Once the deposits are removed inspect for abrasions and missing surface coating i If there are abrasions or missing coating replace ii If all looks well the cylinder may be saved 5 E 6 Muratic acid can be dangerous Follow the manufacturers instructions closely 7 Remove the piston clip with a scribe 8 Remove the piston pin with a piston pin remover INSPECTION NOTE Inspect the piston for abrasions and deposits on the top and sides and clean or replace as necessary E4 Splitting the Cases 1 Remove the fasteners holding the two halves of the crankcase together 2 Separate the cases with a proper case splitting tool 22 CAUTION Take caution when handling the crankshaft It
8. drain hole Using 13 mm wrench remove the oil drain bolt located on the right side of the engine on the clutch cover near the brake lever Item 2 figure 1 NOTE You may need to adjust the brake pedal up or down to access to the drain bolt 4 After it has drained reinstall the bolt being sure that the copper gasket is in place Torque to 15 Nm 11 ft lb 5 Reapply oil from oil fill plug 235 cc Cobra Venom 3 Shoe Clutch Milk or Dexron lIl Automatic Transmission Fluid thru the fill plug NOTE lean bike over onto it s left hand side so that the clutch cover is up unless you have a squeeze bottle 6 Reapply the oil fill bolt hand tight being sure the fiber gasket is in place CAUTION Cobra has spent considerable time and money developing the proper lubrication to handle the harsh environment of the automatic clutch and transmission of this motorcycle Cobra was forced to put forth this effort because the other available options and not adequate Cobra s specially developed Cobra Venom 3 Shoe Clutch Milk Part MCMUGFO1 is the recommended lubricant for your CM50 motorcycle M2 Chain adjustment gt 1 Make sure that the rear wheel is aligned properly 2 Push down on the seat compressing the suspen sion down to where the chain is tightest 3 The chain should not be too tight but not too loose A minimum of 2 5 in of slack should be between the swing arm and the chain M3 Front
9. groove 7 Remove the white cap the fork spring preload sleeve and the fork spring SG NOTE Depressing the fork leg will facilitate removing the white cap 8 The fork can now be turned upside down and drained Assembly 1 Fill the leg with 200 cc 6 8 oz 20 wt fork oil 2 Standard fork oil level is 70 mm 2 75 from the top edge with the fork collapsed NOTE Remove the preload sleeve but leave the spring in for the measurement 3 Install the preload sleeve 4 Install and depress the white cap while installing the spring clip 5 Fork may be reinstalled Engine Service Parts 2003 CM ENGINE ASSEMBLY REFERENCE DRAWING REF 4 PART REF PART DESCRIPTION 1 CAKG0002 Cluth Complete 44 17 0002 Gasket Base 2 CAKG0004_ Shoes Clutch w Washer Springs 45 ECKG0041_ Cylinder 50cc_ CAMU0008_ Spring Set Washer type for Clutch__ _46_ ZCMUORO7 Oring Exhaust Flange N Oring Kit End 60_ ICMU0007_ Stator 66__ ECKG0202_ ReedAssembly 68 0001 Cover Ignition 69 0802 5 8 32x1 3 4 Snap Ring for Piston 80 00204 Kick Starter Dust Shield ECMU0020 Seal Output shaft A A A 2 k 6 8 a 43 8 17 bi NOLSId a2 o d 0 dol SIT ONS dor
10. it to let it cool and spray it with CRC 3 36 or WD 40 If you don t maintain the ignition it is destine to burn up the stator Stator Part 00007 Timing the 2003 50 is very crucial Cobra has found that the best place to set it at 0 050 before Top Dead Center 0 050 before the piston s highest point of travel We do not recommend advancing the ignition timing as it will cause the engine to run very hot in turn causing power loss shortened clutch life and possibly lead to premature stator failure Tools recommended for timing service e Compact motorcycle dial indicator e Universal clutch puller a universal puller that pulls the clutch main drive gear and rotor Part MCMUTL70 TIMING YOUR IGNITION Remove the spark plug cap and sparkplug Insert the dial indicator into the spark plug hole Remove the four 8 32 X 1 34 bolts from the ignition cover Remove the water pump belt from the rotor and water pump shaft Turn the crankshaft counterclockwise until it reaches top dead center Set the dial indicator to zero Turn the crankshaft clockwise until the dial indicator reaches 0 050 1 3 mm from top dead center Line up the lines on the stator and the rotor figure 20 Otherwise loosen the three 10X32 bolts to adjust the stator BONO poc pores eo NOTE If you cannot adjust your stator you must take the rotor off and readjust the timing settings so the lines line up on the rotor and
11. the smooth operation of the throttle cable throttle soundly clacks shut o Check for frayed strands of the throttle cable inside the throttle housing and replace if necessary Check for adequate tire pressures and adjust if necessary Check all nuts and bolts for proper torque and re torque if necessary Spray all moving parts with WD40 or other light oil Check drive chain for Proper tension and adjust if necessary Adequate lubrication and lubricate if necessary o Insure that the ignition stator and rotor are clean and dry o Check the frame for cracks in the metal or cracks in the paint that might indicate that the metal has been stressed beyond it s safe limits Replace or get properly rewelded as necessary o Inspect the rear sprocket damper plate for bending or warping Straighten or replace if more than 1 16 1 6 mm from flat Every 2 hours of operation Replace the transmission oil Every 10 hours of operation o Replace the fork oil o Havethe shock oil replaced by a Certified Cobra Mechanic CAUTION 1 Because of the amount of heat generated by the clutch and engine during extended periods of riding it is advisable to remove the ignition cover afterward to allow the ignition to cool off The heat transfers through the cases and can damage the stator as it cools off because of lack of airflow around the stator If you ever need to weld anything on the bike disconnect the spark plug cap unplug
12. 4 Use fine emery paper on the center hole of the clutch and on the tapered section of the crankshaft 5 Apply a small amount of wicking bearing retainer green thread lock agent to the center tapered section of the crankshaft and taper of clutch arbor 6 Put the clutch back in 7 Apply high strength red thread locking agent to the threads and install the nut and torque to 40 ft lb 54 with the special socket see figure 18 CAUTION Use high strength red thread locker on the threads of the clutch nut If you are using an impact socket just zap it lightly with an air wrench to tighten it because there are only about 4 threads inside the nut and they can be easily stripped If you are tightening it by hand you can very carefully use a 3 4 piece of wooden dowel rod inside the exhaust port to block the piston so you can tighten the nut Do not use something harder than your aluminum piston and do not crush the top of the piston into the ring INSPECTION NOTE There must be in out play in installed clutch 1 5 mm maximum Excess in out will cause early crank seal failure A blue clutch drum is worn out from excessive slippage or improper lubrication Should be no looseness in clutch shoes 31 8 Install the clutch cover taking care to the two longer bolts in their proper locations and tightening in the order specified in figure 19 5mm hex key 5 8 ft lb 7 8 Nm 3 45 mm 1 55 mm Figure 19 9
13. Oil type Cobra Venom 2 cycle Race Oil Fuel oil mix ratios Between 32 1 and 40 1 after engine Break In is complete Carburetion 14 mm Dell Orto Main Jet 92 Slow Pilot jet 55 Float Height 16mm 0 5mm 0 63 0 020 Transmission Speed Single Clutch Cobra 3 shoe Final drive ratio 13 37 T Chain 88 links 420 Transmission clutch oil type Cobra Venom 3 Shoe Clutch Milk or Dexron III Quantity 235 ml 8 00z Chassis Front tire Pressure Rear tire Pressure Front fork Fork oil type Fork oil amount Collapsed fork oil height 2 50 10 15 psi minimum 2 75 10 15 psi min 20 psi for hard pack or rocky conditions Marzocchi 32mm SAE 20 weight 200 6 8 2 oil change 220 ml 7 4 2 rebuild 70 mm 2 75 spring in no spacer Specifications Torque Values Size amp Fastener ft lb Remarks Cylinder head nuts Crankcase bolts Spark plug 14x 1 25 Stator bolts 8 Stator cover bolts E 8 Clutch cover bolts Clutch Engine mount bolts Swingarm Pivot Intake manifold bolts Ignition rotor nut Rear Sprocket Bolts Rear shock mounts Rear Axle Bolt Use green wicking bearing retainer thread locker with primer on the flywheel crankshaft taper but none on the threads Use green wicking bearing retainer thread locker with primer on the crankshaft clutch taper but use red high strength thread locker with primer on the nut SP To apply the proper to
14. Put pipe back on and add oil 225 ml 7 6 0z Cobra 3 Shoe Clutch Milk Part MCMUGFO 1 ES4 Ignition Stator care Stator failure will result from running the bike hot Following is a list of things that will make your engine run hot 1 The timing should not exceed the maximum specifications listed 2 Improper carburetor jetting 3 Improper spark plug heat range Never run a hotter plug than the specified spark plug 4 Clutch slippage See CLUTCH section for causes of slippage CAUTION e Because of the amount of heat generated by the clutch and engine during extended periods of riding it is advisable to remove the ignition cover afterward to allow the ignition to cool off The heat transfers through the cases and can damage the stator as it cools off because of lack of airflow around the stator Spray the stator and rotor with CRC 3 36 or WD 40 and let it drip dry or blow it off a little with an air nozzle e Ignition will overheat if the gap between the rotor and stator is not large enough There should be even clearance as the rotor rotates relative to the stator 32 e Non resistor spark plug caps should be used Resistor caps will result in weaker spark that will reduce performance e Make sure ground wires are secure If the bike is not grounded it will not run e Make sure connections are free of dirt CAUTION If the engine is hot it is EXTREMLY important to take the ignition cover off put a fan on
15. S THAT WEIGH MORE THAT BE SURE THAT THE RIDER ALWAYS WEARS ADEQUATE SAFETY GEAR EVERYTIME HE OR SHE RIDES THEIR COBRA MOTORCYCLE IMPORTANT SAFETY NOTICE A WARNING Failure to follow WARNING instructions could result in severe injury or death to the machine operator a bystander or a person inspecting or repairing the machine CAUTION A CAUTION indicates special precautions that must be taken to avoid damage to the machine NOTE A NOTE provides key information to make procedures easier or clearer Table Of Contents Specifications GBretdl 4 10 Specifications Torque Values 6 Optional CompOLDeblbs eausa CM S NL 7 Break In Procedure oe ee oed Cer 7 Stating Procedure ecce 9 Maintenance 11 Schedule 11 M1 Replacing Transmission Clutch Lubricant esses 12 verus citas te nud 13 M3 Front brake adiustimelib 14 14 M5 Air Filter Cleaning gt eade 15 M6 Fo
16. T to be a throttle blipper 29 CAUTION Sludge build up between the spring washers also keeps the clutch shoe from engaging fully and this will cause the clutch to start to slip So you will need to clean the sludge out or just replace the spring washers and bolts with new ones How quickly this sludge builds up depends on how often you change your oil and whether your rider is a throttle blipper REF PARTNO DESCRIPTION L 6 EcmUoora Guichnut NOTE AFTER THE CLUTCH IS INSTALLED THE CLUTCH DRUM SHOULD HAVE A MIN OF 0 005 INCHES OF IN OUT PLAY IF IT DOSEN T STOCK CAN BE REMOVED FROM THE SHOULDER ON THE ALUMINUM CLUTCH ARBOR FROM THE OPPOSITE SIDE OF THE CLUTCH NUT Figure 18 Clutch Assembly Drawing CLUTCH ASSEMBLY 1 After cleaning or replacing the spring washers reassemble the stack up of washers CAUTION It is important to reassemble the washer stack to that recommended or to your own specialized stack 30 CAUTION It is also important that all three shoes are stacked the same See figure 17 2 Clean the threads of the stack bolt and the clutch with contact cleaner removing all old thread locking material 3 Apply high strength red thread lock material to the stack bolt and tighten as tight as possible without stripping the Allen head CAUTION Avoid allowing excess thread lock material to contact the spring washers and the clutch or the clutch is likely to malfunction
17. chedule will result in long lasting high performance machine e First 72 hour of operation Follow the starting procedure listed this manual Avoid prolonged operation at Wide Open Throttle e After 1 hour of operation o Check for loose bolts and nuts on the bike and retighten as necessary proper toque values are listed under Specifications o Clean the carburetor bowl o Change the transmission clutch lubricant e After 8 hours of operation Change the fork Have Certified Cobra Mechanic change the shock oil e Your bike is now ready for the highest level of competition NOTE During break in the bike will likely loose some engine coolant through the radiator overflow hose Loosing up to 4 oz 120 ml cup is normal Proper coolant level will cover the top of the radiator cores Removing the radiator cap and looking inside is the only way to check the coolant level Never open the radiator cap of a machine that has a hot or warm engine or one that has recently been ridden Burning and scalding could occur CAUTION It is important that the radiator cap is installed correctly and completely otherwise engine damage could occur Starting Procedure Before starting the machine inspect the following Check for proper tire pressure in both tires Observe the chain tension and adjust if necessary Observe the coolant level and fill if necessary Verify that the chain rollers do not have improper wear In
18. cks 20 before you establish the most accurate reading possible e Because of the geometry of the spark plug used in this Cobra Motorcycle the adapter used with your compression tester must have a similar volume protruding into the combustion chamber to establish an accurate value e Length of hose on the compression tester will affect the reading The shorter the hose length the more accurate your reading will be Because of these difficulties in measuring an absolute compression value a useful relative value can be achieved by testing your bike s compression with your own particular gauge after a new top end or when the bike is new so that you know what your particular gauge reads on a fresh engine When it has dropped to 90 of its original value the engine will be down on power and would benefit from a rebuild When it s dropped to 80 it really needs rebuilt Using the table below will help you determine monitor the condition of your top end Engine is Fresh Engine Down Power Engine NEEDS Rebuilt Measured Value Measured Value 0 9 Measured Value 0 8 110 psi 110 psi 0 9 99 psi 110 psi 0 8 88 psi Your Vales 2 Procedure for Compression Testing 1 Shut off the fuel petcock 2 Install the compression gauge into the spark plug hole 3 Hold the throttle to wide open and kick repeatedly approximately 20 times or until the gauge reading does not increase in value with each kick E1 Engine Remo
19. d backwards separately from the wheel After each moto check the 4 rubber dampers spacers and bolts for fatigue You should keep extra rubber dampers in your toolbox part PCMUOO59 Different sized sprockets are also available Watch for bending and warping of the outside rear damper plate If it is bent or warped the rubber dampers in the sprockets do not last as long as when using a straight unit Usually you can straighten the plate with a hammer or just flip it over Changing the rubber dampers 1 Remove the four bolts with the 11mm wrench 2 Take the backing plate off 3 Observe the four rubber dampers and pull the sprocket upward to remove it the sprocket sprocket dampers onto the aluminum studs and sprocket and tighten to 18 ft lb 24 Nm Figure 31 42 1 Pop the four rubber dampers out of 2 Push the rubber dampers into the 3 Place the sprocket with rubber 4 Place backing plate over the dampers 5 nsert the 11mm bolts into the holes Rear wheel pullers Disassembly Figure 32 Rear wheel alignment Figure 33 43 1 Remove axle and back wheel assembly 2 Pull the rear wheel pullers out of the back of the swing arm Measure from the side of the swing arm to the outer edge of the rim and make sure both sides are equal Adjust the wheel pull bolt on the rear wheel puller to get the distance from the swing arm to the rim about the same CS2 Suspension Rea
20. d vertically fill with 2 5 wt often called 3 wt shock oil until 37 38 mm from the top edge 3 Install damper unit into the bottom portion of the shock taking care to not splash out shock oil in the process tighten securely 4 Holding the shock vertical with the bleed valve upward stroke the piston through its complete travel several times slowly and then bleed off any excess air 5 Charge the shock with 230 psig nitrogen 6 Reinstall the spring to the previously measured compressed length and secure with the lock nut 45 Front Forks Figure 35 Because of different rider weights sizes and riding styles we offer various suspension options See Optional Components section of this manual for details on these and other optional components for your Cobra Motorcycle 46 2003 50 FRONT FORK PARTS LIST REFR BESCHIPHON 1 8 956 2 TOPHANDLEBARCLAMP LOWER HANDLE BAR CLAMP 20005 TRIPLE CLAMP UPPER HCBC0806 8 X 30 CS PINCH BOLT FOR TOP TRIPLE CLAMP 8 KCMZo8B INNER FORK CAP WHE 9 70009 O RING UNDER FORK CAP WASHER 47 Troubleshooting 1 2 3 4 5 6 Engine not behaving properly a Carburetor top is installed backwards happens a lot b The carburetor slide indexing pin is missing Engine is down on power a Clutch engagement is not set properly Jetting is incorrect c Silenc
21. e gear as shown in figures 8 amp 9 NOTE If the nut was removed from the input shaft it will be easier to install and tighten later 23 Figure 9 24 10 14 15 16 Insert dowel pins in the left side case as shown in figure 10 DOWEL PINS Figure 10 Apply gasket sealer NAPA Aviation Form A Gasket 765 1210 or equivalent to the mating surfaces of both crankcase halves Apply the crankcase gasket to the left crank case half being sure to install the gasket behind the connecting rod Insert the screws with the three longer ones 40mm long at locations shown 9 30 mm Torque to 9 Nm 80 in the pattern shown in figure 11 Install the piston with new wrist pin bearing and pin and clips Install the piston rings 25 CAUTION Be sure to align the piston such that the arrow on the top piston surface points to the exhaust front of bike engine 17 Apply gasket sealer NAPA Aviation Form A Gasket 765 1210 or equal to the cylinder deck areas around the coolant passage and cylinder studs as shown in figure 12 Sealant around and slightly in the stud holes Sealant around perimeter of coolant pocket Figure 12 18 Install the base gasket 19 Install the cylinder being sure that the piston rings are properly aligned with the indexing pins CAUTION Never force the cylinder If resistance is felt determine the problem and solve it 20 Install the cylinder
22. e side of the swingarm to the frame Remove the engine from the right side of the frame Locate a suitable container for the engine coolant and remove radiator hoses from engine coolant will drain NOTE If the coolant looks to be free of contaminates it may be reused NOTE If you are merely performing a top end service skip ahead to Top End Disassembly Procedure E2 Complete Engine Disassembly Procedure 1 2 3 Remove the magneto cover 9 64 hex key Remove the bolt from the water pump shaft 4mm and slide off the belt cover and the water pump belt Using a flywheel holding tool and 14 mm socket remove the nut that secures the flywheel Using the Cobra flywheel clutch puller 68 remove the flywheel from the crankshaft Remove the stator 9 64 hex key Remove the nut holding the large gear to the transmission input shaft 19 mm socket Remove the special nut starter gear that holds on the clutch special tool available contact your local dealer With the Cobra flywheel clutch puller 68 remove the clutch from the crankshaft details in Clutch Service portion of this manual E3 Top End Disassembly Procedure 1 2 3 Remove the cylinder head nuts 5 16 Remove the outer cylinder head Remove the inner cylinder head 21 INSPECTION NOTE Inspect the cylinder head for deposits and abrasions 1 If there are deposits they should be removed a Black oily
23. er needs repacked Exhaust pipe i Has excess carbon buildup ii Has large dent in it e Compression is low i Piston ii Rings f Reeds are damaged g Ignition timing is incorrect Engine is excessively loud a Silencer needs repacking Engine blubbers at high RPMs a Jetting too rich Engine won t start a Fuel i None in tank ii 15 sour or bad b Carburetor is dirty C Ignition i Spark plug fouled ii Spark plug cap off iii Engine Shut off kill switch is shorted iv Bad electrical ground v Stator winding damaged d Exhaust is plugged Engine won t idle a Idle knob needs adjusted b Carburetor jets are dirty 48 Index Air Filter 15 8 Carburetion Specifications 4 Carburetor ito ias 38 Chain Adjustment 13 Chassis 4 Clutch ens 29 Parts Est oci noises 30 SBIVIG Our ecd 28 Clutch Lubricant Replacing entente 12 Compression test 20 Cooling System 34 Cylinder head TOQUE iiinis ea 6 x ete 42 Engine Parts suse ecards 17 Specifications eerie hae 4 amp ueste i cit Od ORUM 41 Flywheel Gre weet ere ld 6 Fork Oil Replacement
24. includes any appliance with a pilot light Because of the danger of highly flammable liquids do not use gasoline or low flash point solvent to clean the carburetor 1 sure the fuel is shut off 2 Remove the carburetor 3 Drain the fuel in the carburetor 4 Disassemble the carburetor CAUTION Do not use compressed air on an assembled carburetor Or the pressure may deform the float Do not use a strong carburetor cleaning solution which could attack the parts of the carburetor instead use a mild high cleaning solution safe for plastic parts Immerse all the metal parts in a carburetor cleaning solution Rinse the parts in water After the parts are cleaned dry them with compressed air Blow out the fuel passages with compressed air Assemble the carburetor 0 Install the carburetor onto the motorcycle The three most common problems with this carburetor are figure 29 1 Installing the carburetor top backwards and 2 Thecarburetor slide indexing pin falling out 3 Either side vent elbow falling out Figure 29 Proper carburetor top installation and location of rectangular slide indexing pin and one of the elbows that has been known to fall out 40 Reeds The reeds must lay flat on the reed cage If the reed tips aren t lying flat replace them immediately The reeds must have a tight seal on the reed cage If the reed is damaged in any way replace it This means crack
25. is the main power transfer to the rest of the engine If it is out of alignment it will cause premature failure of your bearings which can lead to serious damage to the cylinder and the rest of the engine Do not try to true the crank yourself Truing the crank should be done professionally Cobra trues every crank before it leaves the factory and also welds the pin to keep it true If there are any problems send the engine in or call tech support 330 549 9603 to determine what the problem is CAUTION e f you split the cases check the gear tooth faces for chapping amp signs of fatigue e Check the small needle bearings for fatigue If the bearings are damaged the engine cases should be checked to make sure the needle bearing casing didn t oblong the bearing hole in the case e Needle bearings should be replaced every racing season E5 Engine assembly CAUTION For any seals that are to be installed apply a light amount of grease to the seals ID and a small amount of oil to the OD Press the three bearings into the respective holes in each case half Press in the crank seals such that the concave side faces the crank weights Press in the counter shaft seal concave side faces inside of transmission Install the water pump assembly Wire ring retainer Press in the water pump assembly Tap both ways axially then verify easy rotation Press crank into left case half Insert the transmission input shaft and install large driv
26. ls the clutch main drive gear and rotor Part MCMUTL70O e 5mm T handle Clutch nut removal tool Call local dealer for details Cobra 3 Shoe Clutch Milk Part MCMUGF01 CLUTCH REMOVAL Drain the engine transmission oil 2 Remove the pipe and remove the 6 bolts that hold the kick starter cover on 3 Remove the clutch nut right handed nut on the end of the crankshaft with a 22mm socket 4 Attach the COBRA CLUTCH PULLER There are three 6mm clutch puller holes located on the ends of the center hub figures 15 amp 16 You must use a draw type puller to remove the clutch CAUTION Do not use a jaw type puller or use the 6mm tapped holes as jackscrews or you are likely damage the clutch drum or clutch 5 If necessary apply heat to the center clutch hub CAUTION Do not heat the crankshaft threads or the aluminum shoes 6 Keep tension on the puller as you are heating it A WARNING The clutch will often pop off under tension from the puller and it will be very hot 28 CLUTCH WASHER STACKUPS Once the clutch is removed and cool to touch carefully put it into a vice and remove the center shoulder bolt out of each clutch shoe You will probably have to heat the center hub again to remove the bolts Once you get a bolt loosened carefully remove it with the shoe and observe the way the spring washers are stacked CAUTION It is very important that the clutch stack be reassembled as it was disa
27. mall flat head screwdriver 222 socket E Td MUN 4 33 n 9 va 14 RCMUO016 FLOAT RETAINER PIN RCMUO106 FLOAT BOWL RCMUO201 FLOAT SCRE VELOCITY STACK RCCM0301 Figure 28 38 Your Cobra is equipped with an adjustable carburetor Some fine tuning may be needed according to weather condition and altitude Proper jetting is very important for engine performance and engine life Serious damage to the engine can occur if not properly adjusted IDLE ADJUSTMENT On the left side of the carburetor there are two adjustment screws The larger screw with the knurled head is the idle adjustment screw To raise the idle turn the screw in clockwise in 1 4 turn increments and rev the engine after each adjustment To lower the idle turn the screw counter clockwise TOP END JETTING Indications that the engine is running too rich too much fuel for the air are e Engine not revving out or blubbering at high RPMs e Engine will not clean out Wet or black spark plug NOTE Before changing jetting be sure that the air filter is properly cleaned and has the usual amount of air filter oil An overly dirty air filter can cause the engine to run rich If the engine is running rich on the top end it should be leaned out Leaning it out can be done by 1 Changing the main jet to a smaller number 2 Raising the needle clip this lowers the jet needle one no
28. r in a nonflammable solvent to remove the filter oil Clean the filter in hot soapy water to remove all dirt particles Allow it to dry thoroughly Saturate with filter oil and remove excess Do not clean the air filter with gasoline or other highly volatile petroleum product Diesel fuel or kerosene would be preferred but caution should still be taken Hot soapy water works well oui NOTE The Cobra is equipped with a special designed Air box It is very important to keep the air filter clean and properly oiled with high quality water resistant foam filter oil It s very important to oil your filter consistently each time because varied amounts of oil will change your carburetor jetting NOTE Make sure you change or clean your filter after each moto We recommend carrying 3 or more filters in your toolbox e 1 for practice e 1 foreach moto M6 Fork Oil Replacement Tools required e 5 amp 6mm Allen wrench e 19mm wrench or socket two required e Spring clip remover Disassembly Remove the front wheel Remove the fork legs from the triple clamps Perform the following on one leg at a time Using your hands remove the black rubber plug from the top of the fork leg exposing the white plastic cap 5 Secure the fork leg assembly in a vice by gripping the leg across the flats through which the axle bolt goes through 6 Depress the white plastic cap inwards down and remove the wire spring clip from its
29. r shock 26 e 24 REF DESCRIPTION Because of different rider weights sizes 6 SCMUOS BUSHING and riding styles we offer various suspension options SCMUO305 5 9 ScMUOS22 STOP DISK See Optional Components section of this manual for details on these and other optional components for your Cobra Motorcycle 14 2 00114 LOADER 27 SCMUO321 SPRING 44 Rear Shock Disassembly 1 Bleed the gas pressure from the shock A WARNING Hold a rag over the bleed Schrader valve during this operation as the contents are at extremely high pressure 2 Remove the spring by removing the lock nut and other nut with a large spanner NOTE Measure the distance from the top of the spring to a feature on the top of the shock for repeatable reassembly 3 Using a Pin type spanner separate the top portion of the shock from the bottom NOTE Holding the shock in a vertical manner with the bleed valve down during separation will minimize the amount of oil that is spilled 4 Drain the oil into a suitable container for proper recycling 5 Clean the components of old and contaminates 6 Look for signs of wear and replace if necessary Assembly 1 bleed valve was removed clean the threads of both components apply some Teflon pipe sealant to the threads of the bleed valve and install torque to 10 ft lb 14 Nm 2 With the bottom shock portion situate
30. rk Oil 16 Engine Service Pales geo 17 Engine SEVICE a PSU 19 E1 Engine 20 E2 Complete Engine Disassembly Procedure 21 Top End Disassembly Procedure sse 21 E4 Splitting the Cases er 22 E5 Engine assembly 23 Seat atto S a d A a 28 ESA 32 ES5 Cooling System 34 ES6 Fuel amp Air System i teens 38 A E E E E E E ET 41 Chassis 42 CS1 Wheels 42 GS2 SUSPENSIO sd os acu a ce a che 44 Troubleshooting 48 M NI EN M M IN ODE EI CE 49 Specifications General Dimensions Wheelbase 35 75 908mm Wheel size 10 254mm Seat height 23 9 607 mm Stock T CHJ0001 22 559 mm Optional 0001 Engine Type 2 stroke single cylinder reed valve Cooling system Liquid cooled Displacement 49 8 Bore and stroke 39 mm x 41 7 mm Ignition system Electronic Spark plug Splitfire SF406B 0 023 0 025 0 58 0 64 mm Ignition timing 0 050 1 3 mm Before To Dead Center BTDC Fuel type Sunoco 2 or 93 octane pump gasoline OTHER RACE FUELS ARE NOT RECOMMENDED
31. rque to the spark plug when inserting one must first screw the spark plug in until the metal gasket ring causes resistance and then turn another 1 8 to turn Optional Components e Carburetor jets e Sprockets o Front o Rear Seat with lower seat height 22 559 mm 0001 e Suspension Springs Extrastiff SCMU1400 silver 400 Ib in e Suspension Valving Damping Rate Fork Valving Fork Valving Shock Valving Compression Rebound kit right left Soft fast KCMZ0033A KCMZ0032A SCMU0318A KCMZ0033 KCMZ0032 SCMUO318 Hard slow KCMZ0033B KCMZ0032B SCMU0318B Break In Procedure Your Cobra CM50 is a close tolerance high performance machine and break in time is very important for maximum life and performance The CM50 can be ridden hard after the first 2 hour break in time but it is recommended that no adjustments are made to the carburetion or suspension until the full 8 hours of bike break in has elapsed Also after the engine transmission and drive train have been broken in for the full 8 hours the bike will be faster Use a fuel oil mixture of 32 1 for the full 8 hour break in period Be sure to use 93 octane pump gas or Sunoco 2 with Cobra s specially formulated Cobra Venom 2 cycle Race Oil Part MCMUOLO2 CAUTION Failure to use proper fuel oil or fuel oil mixture may result in premature engine wear or damage to the machine Adhering to the following break in s
32. rt the engine and proceed with riding when the engine is sufficiently warm i e the side of the cylinder is warm to touch CAUTION Never rev an engine full throttle when it s cold or slightly warmed up Cobra recommends that you tell your child to take it easy the first couple of minutes in practice until the engine comes up to full operating temperature Make sure your engine is properly warmed up before racing General Tips Always wear a helmet and other protective riding gear Cobra recommends that you tell your child to take it easy the first couple of minutes in practice until the engine comes up to full operating temperature Make sure your riders foot is not resting on the foot brake while they are riding Evaluate the bikes jetting only after it has been warmed up to race temperatures A properly maintained machine is safer faster and more fun to ride When washing the bike be careful to not directly aim the hose at the bottom edge of the seat or water is apt to enter the airbox Your Cobra Motorcycle has a 10 digit VIN Vehicle Identification Number The first two digits indicate the model and the seventh indicates the model year MY a Example CMxxxx3xxx is a 2003 MY Maintenance Schedule amp Tips It is important that you adhere to this maintenance schedule so as to promote the longevity of your Cobra Motorcycle Between each ride o Check the air filter clean and re oil as necessary o Insure
33. s chips and ruptures Anything abnormal replace the reeds Take the reed cage out and hold it up to the light and look in through the cage If you see light between the reed pedals and the frame then replace the reeds If you do not see light then the reeds should be ok See figure 30 TL coh pean E Ee Figure 30 The presence of light indicates that the reeds should be replaced or possibly turned over ES7 Exhaust The pipe is a crucial element to a motorcycle Any kinks dents or damage done to the pipe will result in a major performance loss NOTE Be sure to take the pipe off and any carbon that may be built up Carbon build up is created from exhaust Exhaust has oils in it and the oils cling to the walls of the inside of the pipe Over a long period of time the diameter of the pipe will decrease due to carbon build up So it is essential to clear the residue CAUTION It is important to repack the silencer Signs of your silencer needing to be repacked are e The bike is louder than normal e A loss of power 41 Chassis Service CS1 Wheels amp Tires Rear wheel Rear wheel dampening Tools recommended for wheel service e 13mm socket e Flathead screwdriver e 11mm wrench or socket e 19mm wrench The Cobra is the only 50 to have the rear wheel damping system This feature prevents engine impact shock caused by hard landings This design allows the cushioned sprocket to move forward an
34. spect the frame for Cracks the metal Cracking paint which might indicate overly stressed material e Verify that the handlebars are tight e Checkthe throttle for Smooth operation and sound closing Frayed strands of the cable inside the throttle housing e Check for loose bolts and nuts and re torque as necessary e X Verify that the air filter is clean and properly saturated with oil e insure that the fuel tank contains an adequate volume of fuel oil mixture to complete the distance required Sunoco MO2X or 93 octane pump gas with Cobra s specially formulated Cobra Venom 2 cycle Race Oil e Turn the fuel on by rotating the fuel petcock knob to the vertically downward position reserve position is horizontally forward CAUTION For best results from your Cobra Motorcycle use only the recommended fuels Testing has shown that most race fuels actually degrade performance When your pre ride inspection is complete the bike may be started For a cold engine follow this procedure 1 Place the motorcycle on a stand of sufficient strength that positions the motorcycle in a level upright position with the rear wheel off the ground 2 Pull up the choke knob and turn it to lock it 3 Kick start the engine 4 Rev the engine in short spurts turning the throttle no more than 1 4 open until the engine will run without the choke 5 Verify a functional engine shut off switch by shutting off the engine 6 Resta
35. ssembled unless new shoes are being installed then it is important to reinstall per figure 17 CLUTCH ASSEMBLY REFERENCE DRAWING REF PART 4 DESCRIPTION 1 0004 Setofthree shoes springs bolts flat washers amp nuts CAMUOO008 Set Of three springs washers bolts amp nuts 0005 Set of three shoes HCBS5603 Single center shoulder bolt E aa 4 nine springs yN Bellville washers zthree flying saucers three dished one flat washer Figure 17 Recommended clutch spring stack Each spring stack contains nine springs Bellville washers six arranged into three flying saucers and three arranged in a dished arrangement against the flat washer Clutch shoe wear e lf the clutch has been slipping and shows signs of glazing it is best to replace the shoes We have found that once the shoes are glazed even if deglazed with emery paper or a file the performance is reduced e The best way to prevent glazing is by not gearing too high changing the oil as specified and by not blipping the throttle Every time you blip the throttle you are working your clutch springs CAUTION The clutch produces a tremendous amount of heat and when a rider is blipping the throttle This makes the clutch and clutch springs wear out quicker This also makes your engine tend to run hotter which decreases engine power and degrades ignition stator efficiency It is important to train your rider NO
36. stator The rotor is not keyed to the crankshaft ROTOR READJUSTING Use the universal clutch puller on the rotor to remove it Insert dial indicator figure 21 Turn the crankshaft counterclockwise so it reaches top dead center Move the crankshaft clockwise to 0 050 1 3 mm before top dead center Inspect and remove markings scratches and thread locker residue from the rotor and crankshaft Sr 33 Figure 20 Lining up the line on the rotor with the line on the stator height for setting ignition timing Figure 21 Using a dial indicator to measure piston ROTOR INSTALLATION 1 Use wicking bearing retainer green thread locker on the inside of the rotor and on tapered part of crankshaft CAUTION It is recommended that you apply the proper thread locking primer to the components that are to receive thread locking material per the manufacturers instructions 2 Eyeball the lines on the rotor and stator then press the rotor onto the crankshaft firmly figure 20 Torque the nut on the rotor to 40 ft lb 54 Nm Recheck the timing following the procedure of timing your ignition Install the water pump belt back on Bolt the ignition cover back on Put the spark plug back in and firmly stick the spark plug cap onto the spark plug ES5 Cooling System TOY OF ee The water pump in the engine keeps the radiator fluid in circulation throughout the motor The air stream running through the radiator cools
37. studs and o rings as shown in figure 13 E gt 4 small o rings combusiton chamber 26 21 22 23 24 25 26 27 28 29 31 Install cylinder head insert Install O rings as shown in figure 14 4 small o rings o inner coolant o ring gt Figure 14 Install the cylinder head and torque to 9 2 ft lb 12 Nm Install stator reinstalling the grommet and wires snug the bolts Install the rotor per Rotor Installation section under the ES4 Ignition portion of this manual Install the water pump outlet pipe apply Ultra black Hi Temp RTV silicon gasket maker to the threads before assembly before installing the clutch and rotate to a vertical position with the engine resting on a bench Install the clutch per Clutch Installation section in this manual Install the coolant drain plug with copper washer 11 ft lb 15 Nm Make sure that the exhaust spacer is on the cylinder 53 in Ib 6 Nm Install the spark plug with a fresh gasket to apply the proper torque to the spark plug when inserting one must first screw the spark plug in until the metal gasket ring causes resistance and then turn another 1 8 to turn Install reed and inlet manifold with new gaskets 58 6 5 Nm 27 ES3 Clutch Cobra clutch puller assembly Clutch puller diagram Figure 15 NT Figure 16 Tools recommended for clutch service e 22mm socket e Universal clutch puller a universal puller that pul
38. tch at a time on the slide Indications that the engine is running too lean are e Engine cutting out on top end e Engine overheating and ultimately seizure e White spark plug CAUTION It is much safer to operate the engine slightly rich as opposed to slightly lean This is because an overly rich engine will just un poorly while an overly lean engine will seize potentially causing an expensive top end rebuild and a DNF To richen the carburetor 1 Change the main jet one number at a time larger 2 Lower the needle clip raising the jet needle one notch at a time until the engine starts to blubber on the top end then move the clip back up one notch or until you get the blubber out FUEL MIXTURE SCREW The smaller brass screw that is towards the front of the engine is a fuel mixture screw This screw will also richen and lean your engine more on the bottom and mid range In warmer conditions turn the screw in In colder conditions turn the screw out Be sure to keep the carburetor very clean and make sure you don t 39 have water or dirt in the carburetor bowl Use automotive carburetor cleaner WD 40 to clean the carburetor inside and out STOCK CARBURETOR SETTINGS The 2003 CM50 stock carburetor settings from the factory are e 55 pilot jet 92 main jet Cleaning the carburetor Clean the carburetor in a well ventilated area and take care that there is no spark or flame anywhere near the working area this
39. the ignition disconnect the kill switch scrape the paint bare near the area to be welded and put the ground clamp as close to the area to be welded as possible Be sure the fuel tank and carburetor have been removed and safely located away from the welding process 3 The frame is 4130 Chrome Moly and it is important to weld it with the proper rod and heat settings set as light as possible Cobra recommends replacing the frame with a new one if the old one becomes damaged 4 If your kick starter lever does not return to the rubber bumper use WD 40 or light penetrating oil under the plastic cover behind the spring on the shaft The shaft is a very close fit to the case and also has an O ring in it and is difficult to get lubrication to which may cause binding If it does not loosen up remove the kick starter cover and kicking assembly Grease the shaft M1 Replacing Transmission Clutch Lubricant Tools needed e 225 ml 7 6 oz Cobra Venom 3 Shoe Clutch Milk Part MCMUGF01 or Dexron Automatic Transmission Fluid e 13mm combination wrench Procedure 1 Begin this procedure with a bike that has been ridden more than 5 minutes but less than 10 minutes It is desired to have the engine warm enough so that the oil runny but not so hot that there is risk of being burned by the engine or the oil A WARNING Hot oil and hot components on the motorcycle may cause burns 2 Lean bike against something or set on stand with oil
40. the radiator fluid Therefore dirty radiators additionally reduce the cooling effect Radiator fluid removal 1 Remove the coolant drain plug A on the front of the engine case figure 22 34 Figure 22 To remove radiator cap 1 Turn the cap counter clockwise to the first stop and wait there for a few seconds 2 Push the cap down and turn it further in the same direction and remove the cap NOTE Inspect the old coolant for visual evidence of corrosion and abnormal smell Fill the radiator up to the bottom of the radiator filler neck with coolant Install the cap turning it clockwise about 1 4 turn Tools recommended for impeller service Flat head screwdriver 5mm hex key 13mm hex wrench 1 8 hex key 9 64 hex key 3 32 hex key Propane torch 3 8 diameter x 8 long steel rod Hammer COBRA IMPELLER SERVICE INSTRUCTIONS 1 Remove exhaust pipe and gas tank you will be using a propane torch in step 12 2 Remove radiator and drain engine coolant by removing the 13 hex head coolant drain plug 3 Ifthe impeller is damaged or broken completely back flush the coolant system to ensure no solid pieces are in the system 4 Remove foot brake 5 Drain engine transmission oil by removing drain screw using a 13mm hex wrench item 2 in the figure below Remove kick starter cover using a 5mm hex key item 3 six places Remove clutch and basket Unscrew water elbow fitting Figure 23
41. val To service the bottom end and transmission the engine must be removed from the frame Tools required 5 16 10 14 22 mm socket 10 13 22 mm wrench 10 17 amp 19 mm sockets 9 64 3 4 amp 5 mm hex key Allen wrench 7 mm nut driver flat or Phillip screwdriver for hose clamps Spring remover Flywheel clutch puller 68 Clutch nut removal tool Call local dealer for details Procedure Remove the seat 4mm hex key Turn of the fuel at the petcock and disconnect the fuel line Remove the tank 5 mm hex key amp 10 mm socket Remove the carburetor from the inlet flat head or Phillips head screwdriver 7 mm nut driver Remove the right side number plate 3mm hex key Remove the silencer amp pipe spring remover 5mm hex amp 10mm wrench Disconnect the ground wire from the reed cage with a 5 mm hex key depending on your ultimate repair you may want to reinstall the fastener in the inlet 8 Leaving the coolant lines connected to the engine remove the radiator from the frame bmm hex with 10 mm wrench 9 Remove the master link from the chain 10 Remove front engine mount bolt 13 mm socket 6 mm hex key 11 To access the swingarm bolt remove brake lever 13 mm wrench 5 mm hex key 12 Remove the swingarm bolt 22mm socket amp wrench nto 20 13 14 Only drive the swingarm bolt far enough to clear the engine leave it holding the on
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