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MAdOR SERVICE MANUAL

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1. Check for defective stator or regulator b If charge rate does not increase Disconnect plug from regulator rectifier and test AC voltage at plug two white wires reading back into alternator Defective Stator or magnet group Voltage reads much less than 28 volts Battery always charging at high rate 1 Check B to Ground voltage with DC voltmeter a If over 14 7 volts DC Regulator not functioning Alternator system okay Check battery charge may be low b If under 14 7 volts DC STATOR B TO STARTER AND IGNITION FLYWHEEL Brat VOLTAGE REGULATOR FIGURE 15 FLYWHEEL ALTERNATOR SYSTEM 14 2 STARTING ELECTRIC STARTER Spec A amp Spec B Normally the starter will require little or no service other than possible brush replacement However if through accident or misuse the starter requires service or overhaul the following information will provide the information necessary to perform this service STARTER DISASSEMBLY Figure 16 Spec A Figure 16A Spec B l Remove the through bolts and separate the end cap the housing and the armature 2 Disassemble the drive assembly and the drive end cap by loosening the self locking nut v 2 2 al gt EN 3 X E 4 another free manual from www searstractormanuals com FIGURE 16A STARTER DISASSEMBLY SPEC INSPECTION OF PARTS Spec
2. ee he o o o9 o9 9 no n n n n Onan Engine Desioen d im es ose Gh ae ao es Ros ROS TRU xe AU ECCE NR Four Cycle Air Cooled Two Cylinder Horsepower at 3600rpm 16 Displacement UC Dec er GS Bey Ae BEES a ena ts WEES 40 3 in GS RAE v ee RT 3 1 8 inch Strokes sce gots lap caer hae he ety cee arya tals een en Sh de A 2 5 8 inch Compression Ratio I UR em AU US deed er OO LS Rec 7 tol Cratnkslhiattw e s ees AR we ud vis sacas woe aros Di QN DRE Ss Horizontal Ductile Iron MalVe s Gee dele Roe welt co a E TR INEO ee MR 05 Mechanical Poppet Bearings Main and Rod ooo o o o m m n nn Sleeve Oil Capacity Roe UE at es RS ARA oy WIN 4 pints Battery Charging System 6 ee 4 4 4 4 ee e e ht onn 12 volt 15 Flywheel Alternator TUNE UP SPECIFICATIONS Tappets 007 009 Exhaust PCT 012 014 Breaker Point Gap Full Separation and Engine Cold 025 Spark Plug 4 ee eee he hiemem hh o hi mom omo ho n n n n n n 025 Ignition Timing Engine Running Hot Setting 21 BTC Engine Not Running Cold Setting 25
3. for left hand cylinder Replace all parts removed in Step 2 Tighten all screws securely Torque manifold bolts to speci fied torque FIGURE 24 VALVE CLEARANCE 19 FLYWHEEL Removing the flywheel is a relatively simple process but the following procedure must be followed to avoid damage to the gear case and possible injury to the operator 1 Turn the flywheel mounting screw outward about two turns WARNING Do not remove the screw com pletely since it acts as a restrain er when the fIywheel snaps loose If the flywheel is not held by the screw the spring action in the wheel will cause it to fly off with great force which can cause injury to the operator Install a puller bar on the flywheel as shown in Figure 25 Turn the puller bar bolts in alternately until the wheel snaps loose on the shaft Do not use a screwdriver or similar tool or pry behind the flywheel against the gear case The gear case cover Is die cast material and will break if undue pressure 1s applied in this manner Unscrew the puller from the flywheel remove the flywheel mounting screw and washer and pull the flywheel off the shaft Take care not to drop the wheel A bent or broken fin will destroy the balance Always use a steel key for mounting the flywheel FLYWHEEL FLYWHEEL PULLER am FLYWHEEL MOUNTING SCREW FIGURE 25 BLOWER WHEEL PULLEY another free manual from www searstractormanuals com GOVERNOR CUP ROLL
4. BTC Preferred setting another free manual from www searstractormanuals com DIMENSIONS AND CLEARANCES All dimensions and clearances given at room temperature of 70 F All values in inches unless otherwise specified CAMSHAFT AND CRANKSHAFT Crankshaft Main Bearing Journal to Bearing Clearance Crankshaft Camshaft Bearing to Camshaft Camshaft Crankshaft Rod Journal to Rod Bearing Connecting Rod End Play PISTON AND CYLINDER Piston Pin in Piston aoaaa aaa a a Piston Pin in Rod Piston Ring Gap in Cylinder Piston Clearance in Cylinder Measured 10 Below Oil Control Ring 90 from Pin Cylinder Bore Standard Size Crankshaft Main Bearing Journal Standard Size Crankshaft Rod Bearing Journal Standard Size TAPPETS AND VALVES Valve Seat Width Valve Face Angle Valve Seat Angle Valve Stem to Guide Intake Valve Stem to Guide Exhaust Tappet to Cylinder Block Clearance Tappet Adjustment Cold intake zv Rx ae aS ER Exhaust z ER Frequently used overhaul values Timing Gear Backlash Oil Pump Gear Backlash Minimum Maximum Vd qe ure ar cst tinte a ri n 0 0025 0 0038 BS ane edere rae t Tu E DA a 0 006 0 01
5. For parts or service contact the dealer from whom you purchased this equipment or refer to your Nearest Authorized Onan Parts and Service Center To avoid errors or delay in filling your parts order please furnish all information requested Always refer to the nameplate on your unit 1 Always give the MODEL and SPEC NO and SERIAL NO Ongn MODEL AND SPEC NO oo md 1 AtOwt IMPORTANT ae CHECK OIL LEVEL DAILY CHANGE OIL EVERY 25 HOURS ot capacity BELOW 32 F SAE 5430 ABOVE 32 F SAE 30 FOR UNUSUAL OPERATING CONDITIONS SEE YOUR SERVICE MANUAL BATTERY 12 For handy reference inset YOUR engine nameplate information in the spaces above another free manual from www searstractormanuals com 2 Do not order by reference number or group number always use part number and description 3 Give the part number description and quantity needed of each item If an older part cannot be identified return the part prepaid to your dealer or nearest AUTHORIZED SERVICE STATION Print your name and address plainly on the package Write a letter to the same address stating the reason for returning the part 4 State definite shipping instructions Any claim for loss or damage to your unit in transit should be filed promptly against the transportation company making the delivery Shipments are complete unless the packing list indicates items are back ordered Prices are purpo
6. Undersize 5 134 2432 Flywheel Includes Ring Gear 114 0225 20 2 020 Unders ize and Magner Ring I 4 0225 30 2 030 Unders ize 6 105 0332 sva 5 RING SET PISTON 104 0032 113 0174 2 Standard 7 105 0004 l Washer Camshaft Gear 113072405 2 005 Oversize Thrust 113 0174 10 2 010 Oversize KEY 113 0174 20 2 020 Oversize 515 0001 2 Camshaft Gear Mounting 1 derer ile 2 30 Oversize Crankshaft Gear Mounting 1 3 917440 40 Oversize 515 0098 Flywheel Mounting Begin 16 114 0228 4 Bolt Connecting Rod Spec D Use with 104 0889 Special Camshaft Only I7 5260017 Washer 7 16 Flywheel 5 15 0002 Flywheel Mounting Spec Mounting Through C Use with 18 870 0137 4 Nut Locking Connecting 104 0763 Camshaft Only Rod Cap 9 105 0388 Camshaft Includes Center 19 850 0055 Washer Lock 7 16 Pin Flywheel Mounting 19 150 0075 Pin Camshaft Cenrer 20 134 2384 Guard Flywheel PISTON AND PIN INCLUDES RETAINING RINGS 2 10420170 Screw Hex Cap _ 112 0134 2 Standard 7 16 14x4 Flywheel 112 0134 05 2 005 Oversize Mounting 112 0134 10 2 010 Oversize 23 518 0014 Lock Crankshaft Gear Washer 112 0134 20 020 Oversize 24 104 0043 Washer Crankshafr Gear 112 0134 30 2 030 Oversize Retaining 112 0134 40 2 040 Oversize 12 112 0122 2 Pin Piston 34 PART PART REF PART NO NO USED DESCRIPTION NO NO USED DESCRIPTION
7. another free manual from www searstractormanuals com MAJOR SERVICE MANUAL AND PARTS CATALOG FOR ONAN 16 HP BF ENGINE SA FOR wee S GARDEN TRACTOR SERVICE BASIC MODEL BF MS 2425 365 0250 Printed in U S A 9AD74 Replaces 8AB73 UJOO S EhUBPUJJO3984J SJE9S UJOJJ 994 494046 another free manual from www searstractormanuals com Ongn SERVICE MANUAL contents FOR BF GARDEN TRACTOR ENGINES WE SUGGEST THIS BOOK BE KEPT HANDY FOR READY REFERENCE EITHER FOR ORDERING PARTS OR MAKING ADJUSTMENTS TABLE OF Ze oZ 779 z gt ATION SPECIFICATIONS DIMENSIONS AN CLEARANCES ASSEMBLY TORQUES Jg m z 2 m j 2 SHOOTING OIL SYSTEM FUEL SYSTEM NITION AND BATTERY CHARGING STARTING SYSTEM ENGINE DISASSEMBLY Q PARTS CATALO ENGINE WIRIN DIAGRAM another free manual from www searstractormanuals com GENERAL INFORMATION This manual contains proper information for the servic ing and overhaul of your Onan engine Use the parts catalog in the rear portion of this book to help you with disassembly and assembly procedures NOTE Flywheel end of engine is considered the front Left and right sides are determined looking at front of engine If it is necessary to contact your dealer or the factory about this engine always supply the complete Model and Spec Number as well as the Ser
8. ly tighten mounting nut A Remove the air intake hose that connects to blower housing This provides an access to view timing mark Rotate the engine clockwise facing flywheel by hand until the 25 BTC mark on gear cover aligns with mark on flywheel Turn another 1 4 turn 90 to ensure points are fully open Using a screwdriver inserted in notch D on the right side of points turn points until gap measures 025 with a flat thickness gauge sure feeler is clean Tighten mounting nut and recheck gap Check ignition timing os manual from www searstractormanuals com q GNITION TIMING QU The timing on the engine is preset at the factory A 1 U non movabl point box is used however a gne timing dhange could be made by adjusting points ihe engine is equipped with an automotive type battery ignition system Both spark plugs fire simultaneously cothus the need for a distributor is eliminated Spark advance is set cold at 25 BTC before top center and should be maintained for best engine performance Always check timing after replacing ignition points or if noticing poor engine performance Proceed as follows Timing Procedure Preferred Method Engine Not Running and Cold 1 Connect a continuity test lamp set across the ignition breaker points Touch one test prod to the breaker box terminal to which the coil lead is connected and touch the other test pro
9. to a value of 4 1 2 6 ft lbs FIGURE 20 BRUSH WEAR LIMIT 7 Brush Spring Inspection Spec only Check brush spring tension as shown in Figure 21 If Do not exceed the rated voltage of the spring tension reads 17 to 25 ounces the spring motor 12 VDC Excessive voltage is satisfactory could demagnetize the motor permanent magnet field 16 w searstractormanuals com another free manual from MOTOR INPUT VOLTMETER 12 CRANKING NOTE Battery to starter wire MOTOR size at least 10 Max length 6 ft AMME TER SWITCH BATTERY FIGURE 22 NO LOAD TEST INSPECTING REASSEMBLED STARTER 1 No Load Test Connect the starting motor as Shown in Figure 22 The values for this test are as follows Spec A Spec B Battery Voltage 11 5 volts 12 0 volts RPM sra herana 8000 rpm min 4 800 6 100 Maximum Current Draw 25 amperes 32 amperes 17 NOTE 1 To ensure good electrical contact make sure starter to engine mounting surfaces are free of dirt or oil 2 When tightening attaching bolts and nut starter gear should be held into ring gear to assure proper backlash 3 Battery to starting motor wire must be tightened securely caution Starter motors are not designed for continuous operation Do not operate more than 30 seconds per ON cycle Do not operate starter more than 10 seconds in a stall condition if engine will not rotate Serious dama
10. 0245 2 TStandard 2 520 0424 6 Cylinder Head 5 16 x 2 5 16 110 0245 02 2 002 Oversize c 520 0759 12 Cylinder Head 5 16 x 2 1 16 110 02 45 05 2 005 Oversize 520 0757 2 Valve Cover 1 4 x 2 1 16 110 0245 10 2 010 Oversize Spec A Through C 10 0245 25 2 025 Oversize 10 104 0776 As Req TShim Rear Bearing Plate 005 29 INSERT VALVE SEAT INTAKE I1 110 1920 2 Gasket Cylinder Head 110 0197 2 TStandard o 12 HEAD CYLINDER 110 0197 02 2 002 Oversize o 110 1924 Right Side 2 Cylinder 110 01 97 05 2 005 Oversize i 110 1925 Left Side 1 Cylinder 110 0197 10 2 010 Oversize t 13 SCREW HEX 110 0197 25 2 025 Oversize 800 0051 5 tBearing Plate Mounting 30 110 1807 4 TGuide Valve 3 8 16 x 1 1 4 3 110 0539 4 Spring Valve 800 0010 2 Valve Cover 144 20 1 3 4 32 110 0639 8 Lock Valve and Spring Begin Spec D Retaining z l4 123 1176 Tube Breather 33 BEARING CRANKSHAFT FRONT 15 BEARING CRANKSHAFT REAR 101 0432 TStandard 101 0420 1 Standard 101 0432 02 002 Undersize 101 0420 02 002 Undersize 101 0432 10 010 Undersize 101 0420 10 Uhdersize 101 0432 20 020 Undersize 101 0420 20 020 Undersize 101 0432 30 030 Undersize 101 0420 30 l 030 Undersize 34 806 0027 2 Screw Hex Head Cap 3 8 16 16 104 0575 2 T Washer Crankshaft Bearing x 3 4 Cylinder Block Thrust 35 526 0066 2 Washer 3 8 Cop
11. 25 CRANKSHAFT 27 821 0014 2 Screw Locking 5 l6 18 3 104 0889 Begin Spec Use 515 0098 x 1 2 Flywheel Guard Flywheel Mounting Key Mounting Only 28 515 0103 Key 1 4 277 104 0763 Spec A Through C Use Crankshaft Stub 515 0002 Flywheel 29 150 1257 Spacer Governor Flyball Mounting Key Only 30 150 0077 Plate Governor Flyball 25 821 0010 3 Screw Locking 174 20 x 1 2 Flywheel Guard Mounting IGNITION GROUP Q REF PART PART Uu NO NO USED DESCRIPTION 160 1158 Assembly Breaker 5 Includes Parts Marked c 2 160 1148 Gasket Breaker Box Cover 503 0311 Clamp Coil Mounting 4 160 1154 Point Set Breaker 6 312 0069 Condenser Breaker Points 9 7 167 0188 Clip Spark Plug Cables 8 160 1150 Gasket Breaker Box Mounting 9 160 1149 Cover Breaker Box 10 160 1151 Plunger T i Spark Plug 19 oil Ignition e 13 167 1462 Cable Spark Plug 16 3 4 nN 14 815 0358 2 Screw Pan Head 8 32 x 5 16 Breaker Box Cover Mounting 2 15 167 0241 2 Plug Spark 16 336 2132 Lead Assembly Points to Coil I7 802 0034 2 Screw Socket Head 1 4 20 x 3 4 Breaker Box Mounting I8 WASHER LOCK o 850 0038 2 Breaker Box Mounting 1 4 850 0025 Condenser Mounting 8 19 SCREW PAN HEAD S 8 15 0403 Condenser Mounting 8 32 5 16 815 0405 Breaker Points Mounting 8 32 x 1 2 20 870 0221
12. A amp Spec B 1 Testing Armature for Grounds Touch armature shaft or core and the end of each commutator bar with a pair of ohmmeter leads If the ohmmeter reading is low it indicates a grounded armature Replace grounded armature See Figure 17 SYSTEM FIGURE 7 TESTING ARMATURE FOR GROUNDS Testing Armature for Short Circuit Use a growler for locating shorts in the armature Place armature in growler and hold a thin steel blade e g hacksaw blade parallel to the core and just above it while slowly rotating armature in growler shorted armature will cause the blade to vibrate and be attracted to the core If armature is shorted replace with a new one Figure 18 Inspecting For An Open Circuit in Armature The most likely place to check for an open circuit is at the commutator riser bars Inspect for loose connections on the points where the conductors are joined to the commutator bars Spec A only HACK SAW BLADE GROWLER FIGURE 18 TESTING ARMATURE FOR SHORT CIRCUITS 15 another free manual from www searstractormanuals com 1 Testing Fieid Coils for Open Circuit Spec A Only Place one lead on the connector and the other on a Clean spot on the brushholder If the ohmmeter reading is high the field coil is open Check the other three brushholders in the same manner See Figure 19 5 Testing Field Coils for Grounds Spec A Only Place one lead on the connector and the other on a clean spot
13. AND REPAIR Figure 5 Removal 1 Remove air cleaner and hose 2 Disconnect governor and throttle linkage choke control and fuel line from carburetor 3 Remove the four intake manifold capscrews and lift complete manifold assembly from engine 4 Remove carburetor from intake manifold IMPORTANT Always work on carburetor in clean conditions Replacing Needle and Valve Seat 1 Wh Remove four screws from top of carburetor and lift off float assembly Invert float assembly as shown in Figure 6 Push out pin that holds float to cover Remove float and set aside in a clean place Pull out needle and spring Remove valve seat and replace with a new one making sure to use a new gasket Install new bowl gasket Clip new needle to float assembly with spring clip Install float Carburetor Float Adjustment Invert float assembly and casting With the float resting lightly against the needle and seat there should be 1 8 clearance between the bowl cover gasket and the free end of the float If it is necessary to reset the float level bend the float tangs near the pin to obtain a 1 8 clearance Figure 6 FIGURE 6 FLOAT ADJUSTMENT Fuel Pump Disassembly Figure 5A 2 3 Remove vacuum line and fuel line Remove the two fuel pump attaching screws Grasp pump and carefully pull apart Diaphragm plunger return spring pump body and mounting gaskets will now be loose Internal fuel pump parts
14. Stator Charging Alternator SCREW HEX HEAD 1 4 20 x 7 16 815 026 3 Blower Housing Mounting 815 0261 4 Cylinder Air Housing Mounting 150 1345 Arm Governor Control 150 1343 Bracket Governor Mounting 150 1398 Spring Throttle Lever Adjusting Screw 152 0155 Swivel Throttle Cable 516 0059 Pin Cotrer Swivel Mounting 518 0176 Clip Throttle Cable 150 1269 Bushing Governor Control 42 NO 16 17 20 2 22 PART NO USED 150 1214 SCREW ROUND HEAD 813 0108 3 812 0066 815 0104 WASHER LOCK 850 0040 2 850 0030 3 850 0045 2 SCREW HEX CAP 800 0028 2 821 0010 2 WASHER FLAT 526 0006 526 0214 526 0113 191 0886 332 0051 AND BLOWER HOUSING GROUP PART DESCRIPTION Spring Governor Stator Mounting 10 32 x 1 1 2 Throttle Lever Adjusting 6 32 x 3 4 Cable Lock Swivel 8 32 x 5 16 Governor Control Mounting 144 Stator Mounting 10 Starter Motor Mounting 5 16 Starter Motor Mounting 5 16 1B x 1 7 Governor Control Mounting 174 20 x 172 Swivel Mounting Governor Control Mounting Starter Moror Mounting Top Hole Regulator Rectifier Clip Fuel Hose her free manual from www searstractormanuals com anot SERVICE KITS AND MISCELLANEOUS REF PART PART NO NO USED DESCRIPTION 168 0 123 Gasket Kit Carbon Removal 168 0124 Gasket Engine 522 0266 Overhau Kit another free ma
15. from preignition Excessive piston wear near the edge of the top ring land indicates pre ignition 2 Connecting Rod Inspection a Replace connecting rod bolts or nuts with damaged threads Replace connecting rods with deep nicks signs of fractures scored bores or bores out of round more than 0 002 Use a new piston pin to check connecting rod for wear A push fit clearance is required and varies from engine to engine If a new piston pin falls through a dry rod pin bore as a result of its own weight replace the rod 22 FIGURE 3l PISTON GROOVE CLEANING FIGURE 3 2 CHECKING RING SIDE CLEARANCE another free manual from www searstractormanuals com FIGURE 33 MEASURING PISTON CLEARANCE 1 Fitting Pistons a Proper piston tolerances must be maintained for satisfactory operation b Measure the piston to cylinder clearance as shown in Figure 33 to be sure the total clear ance follows specifications Fitting Piston Rings a Install the piston ring in the cylinder bore Invert the piston and push the ring to the end of ring travel about halfway into the bore which trues the ring end gap Check the gap with a feeler gauge as shown in Figure 34 b The practice of filing ring ends to increase the end gap is not recommended If the ring end gap does not meet specifications check for the correct set of rings and the correct bore size A cylinder bore that is 0 001 under size will reduce
16. plug gap is set at 025 IGNITION COIL To test primary and secondary windings within the ignition coil proceed as follows 1 Use a Simpson 260 VOM or equivalent 2 Place back lead on ground terminal of coil and red lead to positive terminal Primary resis tance should read 3 87 4 73 ohms 3 Change resistance setting on ohmmeter Place ohmmeter leads inside of spark plug cable holes Figure 13 Secondary resistance should read 12 600 15 400 ohms 4 If any of the above conditions are not met replace coil Refer to Parts Catalog for correct part number OHMMETER FIGURE 13 COIL TEST 13 This engine uses a 12 volt negative ground system Alternator must be connected to battery at all times when engine is run ning Do not reverse battery cables Damage to regula tor or ignition coil could result if cables are reversed Battery Inspection Check battery cells with a hydro meter The specific gravity reading should be approxi mately 1 280 at 80 F Figure 14 If cells are low on water add distilled water and re charge If one cell is low check case for leaks Keep the battery case clean and dry An accumulation of moisture will lead to a more rapid discharge and battery failure Keep the battery terminals clean and tight After making connections coat the terminals with a light application of petroleum jelly or non conductive grease to retard corrosion SPECIFIC 1 GRAVITY READING SHOULD B
17. position it with a driving tool If head of lock pin is damaged use side cutters or Easy Out tool to remove and install new pin Apply oil to thrust washer one used with each bearing to hold it in place while installing the crank shaft Oil grooves in thrust washers must face the crankshaft and washers must be flat not bent The two notches on each washer must fit over the two lock pins to prevent riding on the crankshaft Note Original front bearing uses a separate thrust washer Replacement front bearing is a one piece assembly with thrust washer part of the bearing Do not use a separate thrust washer when installing this teplacement part See Figures 38 and 39 REAR BEARING END PLATE LOCK PIN RN gt ALIGN BEARING OIL HOLES WITH OIL HOLES IN BEAR ING BORE 7 il Vi THRUST 2 WASHER B46 SHIM BEARING PRECISION TYPE DO NOT LINE REAM OR BORE ALIGN BEARINGS NOTCHES WITH LOCK PINS AND MATCH OIL HOLES B49 Rev REPLACEMENT FRONT MAIN BEARING PRECISION TYPE DO NOT LINE BORE OR REAM OR BORE FIGURE 39 FRONT MAIN BEARING INSTALLATION another free manual from www searstractormanuals com MEASURE ENDPLAY HERE REFER TO DIMENSIONS AND CLEARANCES FIGURE 40 CRANKSHAFT ENDPLAY CRANKSHAFT ENDPLAY After the rear bearing end plate has been tightened using the torque recommended in Assembly Torques check the crankshaft endplay as shown in Figure 40 If there is too much endplay see
18. screws alternately until both are tight Attach gear puller to the puller ring and proceed to remove the gear The camshaft and gear must be replaced as an assem bly Before removing the camshaft and gear assembly remove the cylinder head and valve assemblies Then remove the operating plunger for the breaker points and tappets Each timing gear is stamped with O near the edge The pear teeth must mesh so that these marks exactly coincide when the gears are installed in the engine When installing the camshaft gear and shaft assembly be sure that the thrust washer is properly in place behind the camshaft gear Then install the crankshaft retaining washer and lock ring PISTONS AND CONNECTING RODS Observe the following procedure when removing pistons and connecting rods from the engine 1 Drain oil 2 Remove the cylinder head and oil base pan from the engine 3 Remove the ridge from the top of each cylinder with a ridge reamer before attempting piston re moval Figure 29 the piston from cylinder before reaming cause damage to the piston lands the may 4 Turn the crankshaft until the piston is at the bottom of its stroke and remove the connecting rod bolts Lift the rod bearing cap from the rod and push the rod and piston assembly out through 21 the top of the cylinder using a hammer handle Avoid scratching the crankpin and cylinder wall when removing the piston and rod Note Mar
19. the end gap 0 003 CYLINDER BLOCK 1 Make a thorough check for cracks Minute cracks may be detected by coating the suspected area with a mixture of 25 kerosene and 75 light motor oil Wipe the part dry and immediately apply a coating of zinc oxide white lead dissolved in wood alcohol If cracks are present the white coating will become discolored at the defective area Inspect the cylinder bore for scoring Check the Welsh plugs for a tight even fit and the fins for breakage Check the cylinder bore for taper out of round and wear with a cylinder bore gauge telescope gauge or inside micrometer Figure 35 These measurements should be taken at four places the top and bottom of piston ring travel FIGURE 34 POSITIONING OF PISTON RING AND MEASURING OF END GAP 4 Record measurements taken lengthwise at the top and bottom of the piston travel as follows a Lengthwise of the block measure and record as the diameter of the cylinder at the top of the cylinder where greatest ring wear occurs b Also lengthwise of the block measure and record as B the cylinder diameter at the piston skirt travel c Crosswise of the block measure and record as C the diameter of the top of the cylinder at the greatest point of wear d Measure and record as D the diameter at the bottom of the cylinder bore and crosswise of the block e Reading compared to reading and
20. 142 0560 142 056 QTY PART USED DESCRIPTION i Spring Throttle Stop Screw Spring Idle Needle Gasket O Ring Fly Choke Float and Lever Assembly Shaft Float Lever Needle Idle Needle Assembly Power Gasket Set Includes Parts Marked Repair Kit Includes Parts Marked Included in Repair Kit Included in Gasket Set PART NO 149 1322 142 0537 142 0540 149 1323 142 0541 142 0545 149 1326 149 1324 142 0552 142 0555 DESCRIPTION Pump Assembly Complete Valve Plate Assembly Screw Pump Cover Gasket Cover to Valve Plate Gasket Base to Diaphragm Spring Pump Diaphragm Cover Pump Base Pump Plate Pump Spring Diaphragm Pump another free manual from www searstractormanuals com STARTING MOTOR PARTS GROUP SPEC A ONLY REF PART PART NO NO DESCRIPTION 191 0883 Motor Starting Complete 191 0906 Housing Assembly 2 191 0907 Cap Assembly End 3 191 0908 Armature Assembly 4 191 0909 Cap Assembly Drive End 5 19 1 09 10 Drive Assembly Complete 6 191 0911 Bolt Assembly Through 7 191 0912 Brush 8 191 0913 Brush 9 191 0917 Spring Brush 40 another free manual from www searstractormanuals com STARTING MOTOR PARTS REF PART NO NO 191 0933 191 1034 2 191 1045 3 191 1046 4 191 1035 5 191 1047 6 191 1036 7 191 1048 B 850 0040 9 191 1037 10 191 1038 11 191 1039 12 13 l4 1
21. 2 ERE 0 0015 0 0030 Bach ude 0 003 TUO MC ak ten Ghee 0 0020 0 0033 0 002 0 016 zi er wipe wa ae eg 0 002 0 003 0 002 0 005 d 0 0002 0 0004 0 0002 0 0007 0 010 0 020 DEM 0 001 0 003 MELIA 3 1245 3 1255 Ua DEEP 1 9992 2 0000 Quo MAR ee tete CLADE 1 6252 1 6260 Dh vase mrs 1 32 1 8 murum oio cr tte nes 44 ped 45 age 0 0010 0 0025 fec dog erede sg 0 0035 0 0040 us Sete E E Leste 0 0015 0 0030 Pe ne aes EUNT TREE 0 007 0 009 heeds ch te 0 012 0 014 ASSEMBLY TORQUES AND SPECIAL TOOLS BOLT TORQUE FT LB Gearcase 8 10 Cylinder Head Stud Nuts 9 14 16 Rear Bearing Plate Screws 25 27 Starter Mounting Bolts 18 20 Connecting Rod 14 16 Flywheel Cap Screw 35 40 Other 5 16 Cylinder Block Stud and Nuts occaecati cane de nera 8 10 OilBase Mad E s 18 23 Manifold Mounting 6 10 eee Soe te 7 9 The following special tools are available from Onan for further information see Tool Catalog 900 0019 Valve Seat Driver Valve Guide Driver Oil Guide and Driver Combination Bearing Remove
22. 3 Hold throttle in idle position and turn idle adjust ment valve in lean and out rich until engine idles smoothly 4 Reset low speed adjustment idles at 1200 rpm 5 Release throttle engine should accelerate without hesitation If engine does not accelerate properly readjust main fuel valve by turning out slightly No Screw engine Important Do not open more than 1 2 turn beyond maximum power point 10 _ SET LOW SPEED ADJUSTMENT er SO ENGINE RUNS AT 1200 RPM IN SLOW POSITION FIGURE 8 LOW SPEED ADJUSTMENT GOVERNOR Figure 9 These engines are adapted for use where a wide range of speed settings is desired Engine speed is con trolled at any given point between minimum and maximum by simply shifting the throttle lever on the dash panel until the desired speed is reached The design of the variable speed governor gives an automatic decrease in sensitivity when the speed is increased and the result is good stability at all speeds A reliable instrument for checking engine speed is required for accurate governor adjustment Engine speed can be checked with a tachometer Check the governor arm linkage throttle shaft and lever for binding condition or excessive slack and wear at connecting points A binding condition at any point will cause the governor to act slowly and regulation will be poor Excessive looseness will cause a hunting condition and regulation will be erratic Wo
23. 5 16 17 18 19 20 21 22 191 1040 23 191 1041 QTY USED GROUP BEGIN SPEC B PART DESCRIPTION Motor Starting Complete Cover Dust Nut Stop Washer Stop Nut Spring Anti drift Spacer Dust Cover Drive Assembly Screw Hex Cap Starter Through Washer Lock Cap Assembly Drive End Washer Armature Thrust Armature T Spring Brush TBrush Holder Screw and Lockwasher Brush and Brush Holder Mounting T Brush Ground T Stud and Brush Assembly Input T Bushing Insulation Input Stud TWasher Insulation Input Stud TWasher Flat Input Stud fWasher Lock Input Stud Securing Input Stud Cap Assembly Commutator Includes Parts Marked 1 Housing Starter Motor Repair Kit Brush Spring and Stud Includes Parts Marked t Included in the 191 1040 Cap Assembly Included in the 191 1041 Brush Spring and Stud Kit Not Sold Separately 41 another free manual from www searstractormanuals com REF NO 2 Duv du GOVERNOR STARTER CHARGING ALTERNATOR PART QTY PART NO USED DESCRIPTION 150 1350 Rod Governor Control CLIP GOVERNOR CONTROL ROD 518 0004 Carburetor End 870 0278 Governor End 134 2382 Housing Cylinder Left 134 2393 Housing Blower 134 2383 Housing Cylinder Air Right MOTOR STARTING For Components See Separate Group 191 0883 Spec Only 191 0933 Begin Spec 191 0935
24. 8 Breaker Points Mounting Included in Breaker Box Assembly 35 another free manual from www searstractormanuals com FUEL SYSTEM GROUP 36 another free manual from w searstractormanuals com REF NO CS n a PART QTY NO USED 140 1169 142 0558 145 0438 154 1468 154 1446 2 520 0758 4 140 1198 862 00 15 4 503 0664 503 0663 140 1215 140 1213 140 12 16 140 1168 865 0020 505 0086 2 SCREW 800 0008 2 800 0034 4 DESCRIPTION Tube Air Intake Air Cleaner to Blower Housing Carburetor Gasket Carburetor Mounting Manifold Intake Gasket Intake Manifold Stud 5 16 18 x 2 1 2 Intake Manifold Mounting Spec A Through C Support Air Cleaner Nut 5 16 18 Intake Manifold Mounting Spec A Through C Hose Fuel Pump to Carburetor Hose Fuel Pump Vacuum Gasket Air Cleaner Mounting Housing Air Cleaner Element Air Cleaner Cover Air Cleaner Nut Wing 1 4 20 Air Cleaner Cover Nipple 1 2 1 2 Exhaust Carburetor Mountin 1 4 20 x 1 1 4 Intake Manifold Mounting 5 16 18 x 2 1 4 Begin Spec D 37 REF PART QTY NO NO USED I8 WASHER LOCK 850 0040 2 850 0045 4 19 815 0377 3 20 140 1218 22 149 1322 23 518 0328 2 24 809 0045 2 25 800 0003 26 862 0001 27 853 0013 29 149 1321 30 503 0301 3 PART DESCRIPTIO
25. D VALVE BREATHER BAFFLE GASKET FIGURE 3 CRANKCASE BREATHER PRESSURE LUBRICATION Pressure lubricated engines use an oil pump to lubri cate engine parts If oil pressure is low the pump should be checked remove the oil pump it is necessary to detach the intake cup assembly as illustrated in Figure 4 OIL PUMP INTAKE CRANKCASE lt a ON LEFT SIDE FROM INTAKE CUP AT THIS POINT To reassemble reverse the procedure ale FIGURE 4 OIL PUMP ASSEMBLY Check the oil pump thoroughly for worn parts Oil the pump to prime it before reinstalling Except for gaskets and suction cup the component parts of the pump are not available individually Install a new pump assembly if required If new oil pump gaskets are installed they should he Ihe same thickness as those removed A gasket kit with various thickness gaskets is available OIL BY PASS VALVE The by pass valve located to the right and behind gear cover controls oil pressure by allowing excess oil to flow directly back to the crankcase Normally the valve begins to open about 30 psi The valve is non adjustable and normally needs no maintenance To determine if abnormal high or low oil pressure is caused by a sticky plunger inspect as follows 1 Remove 3 8 x 24 x 1 cap screw located behind gear cover and under governor arm 2 Remove spring and plunger with a magnet tool Clean plunger and spring with a suitable solvent and
26. Dimensions and Clearances for minimum and maximum endplay remove the rear bearing end plate and add a shim between the thrust washer and plate Reinstall the end plate making sure the thrust washer and shim notches line up with the lock pins Torque and recheck endplay of the crankshaft Checking Bearing Clearance with Plastigauge 1 Make certain that all parts are marked or identified so that they are reinstalled in their original positions Use heavy fiber or cup grease in space between seals improve seal MOUNTING FACE OF GEAR COVER GEAR COVER FIGURE 4l MEASURING BEARING CLEARANCE Place a piece of correct size Plastigauge in the bearing cap the full width of the crankshaft rod surface about 1 4 inch off center Figure 41 3 Rotate the crank about 30 from bottom dead center and reinstall the bearing cap tighten the bolts to the torque specified in the Table of Torques and Clearances Do not turn the crank shaft 4 Remove the bearing cap Leave the flattened Plastigauge on the part to which it has adhered and compare the widest point with the graduations on the Plastigauge envelope to determine bearing clearance OIL SEALS Figure 42 The bearing plate must be removed to replace the oil seal Drive the oil seal out from the inside Before installing the seals fill the space between lips with a multi purpose grease This will improve sealing REAR BEARING PLATE THIS SURFACE SHOULD BE CLEANED OF AL
27. Do not remove heads when they are hot Warpage may occur another free manual from www searstractormanuals com After removing heads clean out all carbon de posits Be careful not to damage the outer sealing edges where gaskets fit The heads are made of aluminum and can be damaged by careless handling Use new head gaskets and clean both the heads and the cylinder block thoroughly where the head gaskets rest Place heads in position and follow head torque tightening sequence shown in Figure 45 Start out tightening all Nuts to 5 ft lb then 10 ft lb etc until all Nuts are torqued 14 16 ft lb Recheck torque before engine has run a total of 50 hours CYLINDER NO 2 CYLINDER FIGURE 45 CYLINDER HEAD TORQUE SEQUENCE 28 C PARTS CATALOG This catalog applies to tractor application BF Engines Parts are arranged in groups of related items Each illustrated part is identified by a reference number corresponding to the same reference number following the illustration Parts illustrations are typical Unless otherwise mentioned in the description parts are interchangeable between models Right and left sides are determined by facing the blower end front of the engine INSTRUCTIONS FOR ORDERING REPAIR PARTS
28. E 1 280 AT 80 F FIGURE 14 SPECIFIC GRAVITY TEST FLYWHEEL ALTERNATOR Figure 15 This unit is equipped with a permanent magnet flywheel alternator and solid state voltage regulator rectifier output control As with all solid state electrica units precautions are necessary when servicing Observe the following Precautions 1 Do not connect battery cables in the wrong polarity 2 Do not short together alternator stator leads Do not run without a battery Damage will occur to regulator and battery ignition coil Preservice Checks 1 Check for a good ground between equipment and regulator rectifier case Be sure output control plug connector is properly inserted into stator receptacle This means the plug must push in and solidly bottom in the recep tacle to eliminate any resistance due to a poor connection Keep it clean and tight 3 Check battery and is serviceable 9 2 its connection to be sure it NOTE Charging system tests require a fully charged battery another free manual from www searstractormanuals com TESTING BATTERY CHARGING SYSTEM 1 With battery connected check to Ground voltage with DC voltmeter If voltmeter reads 13 8 volts or higher place load headlights on battery to reduce battery voltage to below 13 6 volts Observe ammeter No charge to battery System okay Battery was a If charge rate increases charged fully
29. L OLD SEALING COM POUND BEFORE INSTAL LING SEAL THIS SURFACE SHOULD BE CLEANED OF ALL OLD SEALING COM POUND BEFORE INSTAL LING SEAL GEAR COVER OIL SEAL DRIVE OR PRESS OIL SEAL TO SHOULDER OF THE PLATE BORE REAR BEARING PLATE OIL SEAL FIGURE 42 GEAR COVER AND REAR BEARING PLATE OIL SEALS 26 another free manual from www searstractormanuals com When installing the gear cover oil seal tap the seal inward until it is 31 32 from the mounting face of the cover When installing the bearing plate oil seal tap the seal into the bearing plate bore to bottom against the shoulder in the plate bore Use a seal expander or place a piece of shim stock around the end of the crankshaft when replacing the bearing plate to avoid damaging the seal Remove the shim stock as soon as the plate is in place ASSEMBLY 1 Lubricate all parts with engine oil 2 Position piston on its respective rod and install the pin 3 Install the rings on the pistons starting with the oil control ring Figure 43 Use a piston ring spreader to prevent twisting or excessive expan sion of the ring Some oil control rings and all compression rings have a dot or the word top on one side of the ring to indicate which side faces the top of the piston Unmarked piston rings can be installed either way If the oil control ring has a coil expander install the expander first and then close until the coil ends butt The joint should
30. N Carburetor Mounting 1 4 Intake Manifold Mounting 5 16 Screw Round Head 10 32 x 3 8 Air Cleaner Housing Mounting Wrapper Air Cleaner Element Pump Fuel Clip Bracket Choke Cable Screw Sheet Metal Fuel Pump Mounting 10 x 5 8 Screw Hex 1 4 20 x 1 27 Support to Air Cleaner Nut Hex 1 74 20 Washer Lock 1 4 Cap Fuel Pump Clamp Hose 7 16 See separate group for components a 2 c 2 H tc lt K Lr c 2 a c lt 410 5 1032 354 5 3914 Jauyoue 38 REF PART NO NO 142 0558 142 0532 2 142 0533 3 142 0534 4 142 0535 5 142 0536 6 142 0554 7 142 0538 8 1 42 0064 9 142 0334 10 142 0539 E 142 0539 12 142 0559 13 142 0553 14 142 0543 15 149 1326 another free manual from www searstractormanuals com PART USED DESCRIPTION Carburetor Assembly Complete Body Assembly Lower Sleeve Assembly Shaft Throttle Packing Shaft Shaft Choke Clip Float Valve Fly Throttie Screw Throttle Stop Screw Fly Mounting Screw Bow Cover Mounting Screw Plate Mounting Gasket Plate Valve Assembly Float Gasket Plate Carburetor Inlet FUEL PUMP PARTS GROUP REF NO 2 3 4 5 6 7 8 9 39 REF PART NO NO 16 142 0544 17 142 0282 18 142 0550 19 142 0546 20 142 0547 21 142 05 48 22 142 0016 23 142 0549
31. PIN ROTATE GOVERNOR CUP SO THAT ROLL PIN FITS INTO THE METAL LINED HOLE IN THE CUP GOVERNOR GOVERNOR SHAFT YOKE Smooth Side Toward Cup IF FEELER WILL ENTER HOLE 1 2 BALL HAS FALLEN OUT FIGURE 26 GEAR COVER ASSEMBLY GEAR COVER Figure 26 After removing the mounting screws tap the gear cover gently with a soft faced hammer to loosen it When installing the gear cover make sure that the pin in the gear cover engages the metal lined smooth hole in the governor cup Turn the governor cup so that the metal lined hole is at the three o clock position The smooth side of the governor yoke must ride against the governor cup Turn the governor arm and shaft clockwise as far as possible and hold in this position until the gear cover is installed flush against the crankcase Be careful not to damage the gear cover oil seal Adjust the roll stop pin to protrude to a point 3 4 from the cover s mounting surface GOVERNOR CUP With the gear cover removed the governor cup can be taken off after removing the snap ring from the camshaft center pin Catch the flyballs while sliding the cup off Figure 27 Replace with a new part any flyball which is grooved or has a flat spot the ball spacer if its arms are worn or otherwise damaged and the governor cup if the race surface is grooved or rough The governor cup must be a free Spinning fit on the camshaft center pin but without any excessive pla
32. all Bearing Governor Shaft 526 0065 5 Gear Cover Mounting 9 509 0040 Seal Gear Cover Copper 5 16 10 103 0408 Gasket Gear Cover Mounting 27 SCREW HEX CAP 11 516 0011 2 Pin Gear Cover 5 16 x 800 0026 2 Oil Filter Pad Cover Mounting 1 1 8 5716 18 x 3 4 12 123 1138 Cap and Indicator Oil Fill 800 0056 4 Oil Base to Block 3 8 16 x 13 102 0693 Gasket Oil Base Mounting 2 1 2 14 505 0056 2 Plug Oil Drain 800 0032 4 Gear Cover Mounting 5 16 18 15 102 0730 Base Oil x 1 3 4 16 120 0140 Spring Oil By Pass Valve 800 003 4 Gear Cover Mounting 5 16 18 17 801 0050 Screw Oil By Pass x 2 1 4 3 8 24 x 1 800 0007 2 Oil Pump Mounting 174 20 x 18 120 0398 Valve Oil By Pass 19 120 0491 Pump Oil Complete Included in Gear Cover Assembly Note Internal parts not sold separately 20 120 0713 Intake Oil Pump Includes Cup Screen and Pipe another free manual from www searstractormanuals com 33 another free manual from www searstractormanuals com CRANKSHAFT FLYWHEEL CAMSHAFT AND PISTON GROUP REF PART REF PART QTY PART ND USED JESCRIPTION NO USED DESCRIPTION 150 0078 Ring Camshaft Center Pin 13 518 0311 4 Ring Piston Pin Retaining 2 150 1116 Governor 14 ROD ASSEMBLY CONNECTING 3 510 0015 5 Ball Fly Governor 114 0225 2 Standard 4 104 0779 Gear Ring Flywheel 114 0225 10 2 010
33. are available in a repair kit Check Parts Catalog for correct part number 5 Ensure that clamps are replaced on fuel line CAUTION Use care when reassembling pump all parts must be perfectly aligned or pump will leak creating a fire hazard CARBURETOR ADJUSTMENTS The carburetor has a main fuel valve adjusting screw and an idle valve adjusting screw Figure 7 A low another free manual from www searstractormanuals com speed adjustment screw is shown in Figure 8 Initial Adjustment 1 Turn main fuel valve clockwise until it just closes 2 Now open main fuel valve 1 1 8 turns counter clockwise 3 Close idle valve in same manner and open it 1 2 to one turn counterclockwise 4 This initial adjustment will permit engine to start and warm up prior to final adjustment Valves may be damaged by turn ing them too far MAIN FUEL HIGH SPEED ADJUSTMENT LOW SPEED SET ON GOVERNOR LINKAGE SMALL GAP HERE AT NO THROTTLE STOP SCREW SIDE VIEW IDLE ADJUSTMENT REAR VIEW FIGURE 7 MAIN FUEL AND IDLE VALVE ADJUSTMENT Final Adjustment 1 Turn main fuel valve in until engine misses lean mixture then turn it out past the point where engine runs smoothly until engine runs unevenly rich mixture Turn valve to mid point between ean and rich so engine runs smoothly Hold engine at idle position and set low speed adjustment screw Figure 8 until a fast idle is obtained 1200 rpm
34. be 180 from the gap of that ring FIGURE 43 PISTON RINGS INSTALLATION OF PISTON IN CYLINDER 1 Turn the crankshaft to position the number one rod bearing journal at the bottom of its stroke 2 Lubricate the number one piston assembly and inside of the cylinder Compress the rings with a ring compressor as shown in Figure 44 3 Position the piston and rod assembly in the cylinder block NOTE The connecting rod numbers should always face away from the camshaft or bottom side of engine INSTALLING PISTON FIGURE 44 4 Tap the piston down into the bore with the handle end of a hammer until the connecting rod is seated on the journal Figure 44 Install the bearing cap on the rod with the witness marks and stamped reference numbers matching the marks on the rod Install and tighten the bolts to the specified torques The bearing cap must be tapped several times to properly align it with the rest of the connecting rod Clearance varies on the journal if this is not done Install the remaining pistons and rods in the same manner Crank the engine over by hand to see that all bearings are free 5 Install the oil base with a new gasket 6 Install the cylinder heads and torque 14 16 ft Ib 7 Replace oil and break in engine CYLINDER HEADS Remove the cylinder heads for cleaning if poor engine performance is noticed Use a 1 2 inch socket wrench to remove cylinder head nuts Lift heads off CAUTION
35. crankcase Do not use only when engine is warm Exception Drain initial service DS oil Do not mix brands oil fill at 25 operating hours or grades of motor oil Engine damage could result from mixing non compatible oils To drain remove the 1 2 inch pipe plug on the rear corner of the oil base After oil drains replace the pipe plug and refill crankcase with 4 pints 4 1 2 if equipped with filter of a good quality detergent oil Oil must meet or exceed the API American Petroleum Institute designation SE or SE CC this oil was formerly designated as MS MS DG or MS DM Figures 1 and 2 For temperatures above 30 F use SAE 30 oil for temperatures below 30 F use 5W30 or LOW In extremely dusty conditions or in very cold weather change oil at least every 25 hours of operation ALWAYS REPLACE TIGHTLY OR OIL LEAKAGE MAY OCCUR OIL DRAIN BOTTOM SIDE REMOVE 1 2 INCH PIPE PLUG TO DRAIN FIGURE 2 OIL DRAIN LOCATION FULL CAUTION DO NOT OVEFEFILI ADD ONE RINT Crankcase Breather This engine uses a crankcase breather valve for maintaining crankcase vacuum No maintenance is generally required If the crankcase becomes pressurized as evidenced by oil leaks at the seals clean baffle and valve in a suitable solvent FIGURE 1 CRANKCASE OIL FILL See Figure 3 tiai another free manual from www searstractormanuals com FLAT WASHER BREATHER HOSE ACORN NUT N SPRING FLAT WASHER REE
36. d to a good ground on the engine EMERGENCY PREFERRED METHOD REMOVE HOSE AND VIEW TIMING MARKS THROUGH THIS HOLE CORRECT TIMING IS 21 HOT SETTING ENGINE RUNNING 25 BTC COLD SETTING STATIC FIGURE IGNITION AND TIMING ADJUSTMENT Timi Ly Turn crankshaft against rotation cotunterclock wise until the points close Then slowly turn the crankshaft with rotation clockwise The lamp should go out just as the points break which is the time at which ignition occurs 25 BTC ng Procedure Engine Running and Hot To accurately check the ignition timing use a timing light when engine is running Connect the timing light according to its manufacturer s in structions Either spark plug can be used as they fire simultaneously Remove the air intake hose that connects to blower housing to provide an access to view timing marks warning sure tractor is the neutral positron before starting engine Start the engine When engine warms up check the ignition timing The mark on the flywheel should line up with the 21 mark on the cover Replace hose breaker box cover and any other hardware removed from engine another free manual from www searstractormanuals com SPARK PLUG GAP 0 025 GASOLINE FIGURE 2 SPARK PLUG GAP SPARK PLUGS Figure 12 Remove both spark plugs and install new ones every 100 hours Use ONAN No 167 0241 or Champion H 8 Check to be sure spark
37. er installing New camshaft bearings are precision type which do not require line reaming or line boring after installation Coat the bearing with SAE20 oil to reduce friction Place the bearing on the crankcase over the bearing bore with the elongated hole in proper position and narrow section facing out except bores without oil holes install with bearing groove at the top Be sure to start the bearing straight Press the front bearing in flush with the outside end of the bearing bore Press the rear bearing in flush with the bottom of counterbore which received the expansion plug see Figure 37 PRECISION TYPE DO NOT LINE REAM OR BORE ALIGN HOLE IN BEARING e 7 32 FROM OUTSIDE WITH HOLE IN BEARING BORE CAMSHAFT BEARING FIGURE 37 CAMSHAFT BEARING Crankshaft main bearings are precision type which do not require line reaming or line boring after installa tion They are available in standard size and 002 undersize Expand the bearing bore by placing the casting in hot water or in an oven heated to 200 F CAUTION If torch is used apply only a little heat Distortion will result from too much local heat To ease assembly cool the precision bearing to shrink it Align the oil hole s in the bearing with the oil hole s in the bearing bore The oil passage must be at least 1 2 open Lubricate bearings with SAE 20 oil before installing The cold oiled precision bearing should require only light taps to
38. est method but a telescoping gauge can be used Check the size at six places in the bore measure twice at the top middle and bottom at 90 angles The ctosshatch formed by the scratching of the stones should form an angle of 23 This can be achieved by moving the hone up and down in the cylinder about 40 cycles per minute Figure 36 Clean the cylinder block thoroughly with soap water and clean rags A clean white rag should not be soiled on the wall after cleaning is com plete Do not use a solvent or gasoline since they wash the oil from the walls but leave the metal particles Dry the crankcase and coat it with oil AVOID THIS FINISH CROSSHATCHING 24 another free manual from www searstractormanuals com CRANKSHAFT Inspect the bearing journals If they are scored and cannot be smoothed out by dressing down replace the crankshaft Whenever making major repairs on the engine always inspect the drilled passages of the crankshaft Clean them to remove any foreign material and to assure proper lubrication of the connecting rods BEARINGS Figures 37 39 Removing camshaft or crankshaft bearings requires complete disassembly of the engine Use a press or a Suitable drive plug to remove the bearings Support the casting to avoid distortion and avoid damaging the bearing bore during removal and installation Use oil on the bearings to reduce friction when installing and again lubricate with oil aft
39. ge could result if these time limits are exceeded another free manual from www searstractormanuals com ENGINE DISASSEMBLY VALVE SYSTEM Properly seated valves are essential to good engine performance The aluminum cylinder heads are remova able for valve servicing Do not use a pry to loosen the cylinder head rap sharply on the edge with a soft faced hammer taking care not to break any cooling fins A conventional type valve spring lifter may be used when removing the valve spring locks which are of the split type Clean all carbon deposits from the cylinder heads piston tops valves guides etc If a valve face is burned or warped os the stem worn install a new valve Refer to Figure 23 Worn valve stem guides may be replaced from inside the valve chamber Valve locks are split tapered type the smaller diameter of which must face toward the valve head Tappets are also replaceable from the valve chamber after first removing the valve assemblies The valve face angle is 44 The valve seat angle is 45 This 1 interference angle results in a sharp seating surface between the valve and the top of the valve seat The interference angle method of grinding valves minimizes face deposits and lengthens valve life The valves should not be hand lapped if at all avoid NOTE USE A STANDARD AUTOMOTIVE TYPE WRENCH TO ADJUST THE TAPPETS able because the sharp contact may be destroyed This is especially importa
40. ial Number shown on the engine nameplate The engine nameplate is located on left side of blower housing end opposite oil filter Refer to the Troubleshooting Guide for assistance in locating and correcting troubles which may occur If a major repair or overhaul becomes necessary the engine should be carefully checked and necessary repairs made by a competent mechanic Maintain factory limits and clearances as shown replacing worn parts when necessary WARNING Onan ENGINE MODEL REFERENCE Identify your model by referring to the MODEL and SPEC specification NO as shown on the unit name plate Always use this number and the engine serial number when making reference to your engine How to interpret MODEL and SPEC NO BF MS 0123 A I 2 4 Factory code for general identification purposes 2 Specific Type S MANUAL STARTING MS ELECTRIC STARTING 3 Factory code for optional equipment supplied 4 Specification Spec Letter advances with factory production modification uses this symbol throughout this manual to warn of possible serious personal injury This symbol refers to possible equipment damage WARNING TO AVOID POSSIBLE PERSONAL INJURY OR EQUIPMENT DAMAGE AN AUTHORIZED SER VICE REPRESENTATIVE MUST PERFORM ALL SERVICE w searstractormanuals com another free manual from SPECIFICATIONS Engine Manufacturer
41. k each piston and rod assembly so they can he returned to their respective cylinders after overhaul Keep connecting rod bearing caps with their respective rods 5 Remove the piston rings from the piston with a piston ring spreader as shown in Figure 30 Remove the piston pin retainer and push the piston pin out Remove dirt and deposits from the piston surfaces with an approved cleaning solvent Clean the piston ring grooves with a groove cleaner or the end of a piston ring filed to a sharp point Figure 31 Care must be taken not to remove metal from the groove sides CAUTION Do not use caustic cleaning solvent or wire brush for cleaning pistons These materials will cause piston damage FIGURE 29 REMOVING RIDGE FROM THE CYLINDER another free manual from www searstractormanuals com When cleaning the connecting rods in solvent include FIGURE 30 REMOVING PISTON RINGS the red Blow out all passages with compressed air Inspection The following text contains inspection procedures conceming pistons and connecting rods 1 Piston Inspection a Inspect the pistons for fractures at the ring lands skirts and pin bosses Check for wear at the ring lands using a new ring and feeler gauge as shown in Figure 32 Replace the piston when the side clearance of the top com pression ring reaches 0 008 Replace pistons showing signs of scuffing scoring worn ring lands fractures or damage
42. nt where stellite faced valves and seats are used Valve faces should be finished in a machine to 44 Valve seats should be ground with a 45 stone and the width of the seat band should be 1 32 to 3 64 wide Grind only enough to assure proper seating Remove all grinding compound from engine parts and place each valve in its proper location Check each valve for a tight seat using an air pressure testing tool If such a tool is not available make pencil marks at intervals across the valve face and observe if the marks rub off uniformly when the valve is rotated part of a turn against the seat Lightly oil the valve stems and assemble all parts removed The positive type valve rotators prolong valve life and decrease valve repairs When functioning properly the valve is rotated a fraction of a turn each time it opens While at open position the valve must rotate freely but in only one direction If rotators are faulty install new rotators NOTE SEE VALVE TAPPET ks ici IN TEXT VALVE ADJUSTING SCREW VALVE ROTATOR VALVE SPRIN VALVE t trang WASHER LOCK INTAKE VALVE ONLY FIGURE 23 VALVE SYSTEM w searstractormanuals com another free manual from Tappet Adjustment The engine is equipped with ad justable valve tappets The valve tappet clearance should be checked and adjusted if necessary at least every 400 operating hours or when poor engine perform ance is noticed Adjust the
43. nual from www searstractormanuals com MOUNTED BEHIND BLOWER WHEEL ALT STATOR FUSE 35 AMP AMMETER OPTIONAL J DISCONNECT SWIT CH START SWITCH 22 IGNITION SWITCH BATTERY STARTER 12 VOLT FURNISHED BY CUSTOMER ENGINE WIRING DIAGRAM CAUTION REGULATOR MUST BE GROUNDED THROUGH MOUNTING BOLTS OPTIONAL TO ELIMINATE 125 MA LEAKAGE ON SHUTDOWN BREAKER AND CAP ASSEMBLY IGNITION sie ii COIL ET 1 IL x SPARK 44 UJOO S EhUBPUJJO3984J SJE9S UJOJJ 994 494046 another free manual from www searstractormanuals com ONA 1400 73RD AVENUE MINNEAPOLIS MINNESOTA 55432 A DIVISION OF ONAN CORPORATION
44. on the frame after unsoldering shunt field coil wire If the ohmmeter reading is low the fields are grounded either at the connector or in the windings FIGURE 21 TESTING BRUSH SPRING TENSION STARTER ASSEMBLY Reassembly is the reverse of disassembly When re assembling observe the following l Wipe off any dirty parts with a clean cloth or blow clean using filtered compressed air NOTE Bearings must not be immersed in cleaning fluid These parts should be cleaned with a brush dipped in clean engine oil 2 Apply SAE 10W 30 oil on the armature shaft spline and bearings FIGURE 19 TESTING FIELD COILS FOR OPENS 6 Brush Inspection If brushes are worn shorter than REASSEMBLY Spec B only 1 4 inch replace them Check to see that brushes l Assemble brushes so that chamfered side is away move smoothly in the brush holders See Figure 20 from the brush springs and position the brush shunts so that they will not contact the commuta tor or commutator end cap 2 Torque bolts Figure 16 a item 3 to a value of 3 3 1 2 ft Ibs 3 Torque nut Figure 16 a item 4 to a value of 4 5 ft lbs 4 Apply a thin film of grease to the commutator end of the armature shaft and to the portion of the shaft that contacts the bearings Apply a generous film of Lubriplate Aero grease to the shaft thread Torque stop nut Figure 16 a item 1 to a value of 20 25 ft lbs Hold armature in a vise 6 Torque thru bolts Figure l6 a item 2
45. per 17 101 0415 TGasket Bearing Plate Cylinder Block I8 101 0439 Y Gearing Excludes 36 110 0068 2 Gasket Valve Guide Intake Bearing 37 517 0120 Breather Hole 19 101 0405 2 f Bearing Camshaft Precision 4 20 509 0041 TSeal Bearing Plate F Included in Cylinder Block Assembly 21 516 0072 4 Pin Main Bearing Stop Replacement front flange bearing replaces unflanged bearing and thrust washer another free manual from E another free manual from www searstractormanuals com GEAR COVER OIL BASE AND OIL PUMP GROUP 32 REF PART REF PART QTY PART NO NO USED DESCRIPTION NO NO USED DESCRIPTION COVER ASSEMBLY GEAR Includes Parts 21 120 0161 Gasket Oil Pump Marked 22 149 1299 Tube Fuel Pump Vacuum 103 0501 Begin Spec D 23 WASHER LOCK 103 0409 Spec A Through 850 0050 4 Oil Base Mounting 3 8 2 510 0105 Bearing Governor Shaft 850 0040 2 Oil Pump Mounting 1 477 3 SHAFT amp ARM ASSEMBLY GOVERNOR 24 122 0359 Cover Oil Filter Pad 150 1470 Begin Spec D 25 122 0321 Gasket Oil Filter Pad Cover 150 1349 Spec A Through 26 WASHER FLAT 4 150 1187 Yoke Governor Shaft 526 0122 2 Oil Filter Pad Cover Mounting 5 815 0046 2 Screw Yoke Retaining 5 16 6 516 0130 Pin Governor Stop 526 0066 Oil Pressure Relief Valve 7 509 0008 Seal Oil Governor Shaft Screw Copper 3 8 8 510 00 14 B
46. r Main and Cam Combination Bearing Driver Main and Cam Flywheel Puller ENGINE TROUBLESHOOTING Valve Sensitivity Too Great Gap Serin oken Sa wired Fin ION SYST TROUBLESHOOTING Bye athe GASOLINE ENGINE STARTING SYSTEM IGNITION SYSTEM Gasket INTERNAL ENGINE Quality Fuel Oily Coolin Blown Head Gasket Thermostat Gaskets LUBRICAT OF THROTTLE AND GOVERNOR Carburetor Cinnkcase Ait Cleaner Head COOLING SYSTEM AIR COOLED COOLING SYSTEM WATER COOLED er Passages Rest Loose or Corroded Battery Connection Rich Fuel Mixture or Choke Stuck Engine Floodfed Bad ignition Coil Condenser Poor Valve or Valve Seal Leaking Piston Rings Worn or Br Worn Water Pump or Pum insufficient Cool ant Defective Fuel Pump Fault Faulty Sta ter Faulty Start Solenoid Worn Points or improper Out of Fue Check Relief Va Governor Linkage Binding Defect Dir Dut Defective Linkage Wom or Disconne Wa sd EL H ELS EI e ae uw Vl s ahr ied aoe Qe Jele jejejejeje Jo el I BIOBBZSENE eleje EEBESSDEB 114444 3914 Jeuyoue another free manual from www searstractormanuals com OIL SYSTEM CRANKCASE OIL Change crankcase oil every 50 operating hours and caution 20 not overfill
47. reading C compared to reading D indi cates cylinder taper another free manual from www searstractormanuals com FIGURE 35 METHOOS OF MEASURING THE DIAMETER OF A CYLINDER f cylinder taper exceeds 0 005 rebore and hone to accomodate the next oversize piston Reading compared to reading and reading B compared to reading D indi cates whether or not the cylinder is out of round If the out of round exceeds 0 002 the cylinders must be rebored and honed for the next oversize piston A reboring machine is used when going lo oversize pistons The following repair data covers honing to oversize by use of a hone REPAIR 1 2 Anchor the block solidly A hone can be used to refinish a cylinder for either vertical or horizontal honing Use either a drill press or heavy duty drill which operates at approximately 250 to 450 rpm Connect drill to hone and start drill Move the hone up and down in the cylinder approximately 40 cycles per minute Usually the bottom of the PRODUCE CROSS HATCH SCRATCHES FOR FAST RING SEATING FIGURE 36 cylinder must be worked out first because it 15 smaller Then when the cylinder takes a uniform diameter move the hone up and down all the way through the bore Follow the hone manufacturer s recommendations for wet or dry honing and oiling the hone Check the diameter of the cylinder regularly during honing A dial bore gauge is the easi
48. reinstall another free manual from www searstractormanuals com FUEL SYSTEM CARBURETOR CLEANING AND INSPECTION To clean the carburetor soak all components thoroughly in a good carburetor cleaner following the manufac turer s instructions Be sure to remove all carbon from carburetor bore especially in the area of the throttle valve After soaking clean out all passages with filtered compressed air Check the adjusting needles and nozzle for damage If float is loaded with fuel or damaged replace it The float should fit freely on its pin without binding Check the choke and throttle shafts for excessive side play and replace if necessary Note Carburetor repair and gasket kits are available from your nearest Onan Parts Center CHOKE FLY CHOKE SHAFT AND LEVER NOTE ON SOME MODELS ENGINES FUEL PUMP IS MOUNTED DIRECTLY TO CARBURETOR Ss FLOAT LEVER GASKET CARBURETOR INLET PLATE FUEL INLET FLOAT VALVE ASSEMBLY FLOAT AND LEVER ASSEMBLY MAIN ADJUSTING NEEDLE x CARBURETOR BODY IDLE ADJUSTING NEEDLE THROTTLE STOP SCREW THROTTLE SHAFT AND LEVER THROTTLE FLY FUEL LINE FIGURE 5 EXPLODED VIEW OF CARBURETOR another free manual from www searstractormanuals com DIAPHRAGM GASKET PLATE PUMP SPRING SPRING PUMP BASE PUMP COVER GASKET EXPLODED VIEW OF FUEL PUMP FIGURE 5A EXPLODED VIEW OF FUEL PUMP CARBURETOR DISASSEMBLY
49. rethane precleaner that must be removed cleaned and oiled every 25 hours of operation or more under extremely dusty conditions 1 To clean pre cleaner wash in water and detergent referring to Figure 10 Remove excess water by squeezing like a sponge and allow to dry thorough ly Distribute three tablespoons of SAE 30 engine oil evenly around the pre cleaner Knead into and wring excess oil from pre cleaner Depending on conditions in which the tractor is operating the inner paper element should be re placed whenever it becomes excessively dirty or oily CAUTION Never run the engine with the air cleaner removed Dirt will enter the engine and score the cylinders WASH SQUEEZE DRY COAT WITH OIL INSTALL OVER PAPER ELEMENT FIGURE 10 AIR CLEANER ASSEMBLY 1l IGNITION AND BATTERY CHARGING BREAKER POINTS To maintain maximum efficiency from the engine change the breaker points every 200 hours of operation Proceed as follows when engine is cold Remove the two screws and the cover on the breaker box Remove the two spark plugs so engine can be easily rotated by hand Check condition of spark plugs at this time Refer to Figure 11 Remove mounting nut A and pull the points out of the box just far enough so screw B can be removed and leads disconnected Remove screw C and replace condenser with a gt new one Replace points with a new set but do not complete
50. rk the arm back and forth several times by hand while the engine is idling to check for above conditions If governor is hunting or not operating properly adjust as follows and as shown in Figure 9 1 Disconnect linkage A from one of holes C 2 Push linkage A and governor arm B as far back toward carburetor as they will go 3 Holding linkage and governor arm toward direction of carburetor insert end of linkage into whichever hole C in governor arm lines up the closest The governor control spring is factory set in the top hole of the governor control shaft bracket To increase the sensitivity move the spring loop into the hole nearest the control shaft To decrease the sensitivity move the spring outward After the sensitivity has been set adjust the low speed with the adjustment Screw on the control wire bracket another free manual from www searstractormanuals com THROTTLE STOP SCRE CARBURETOR THROTTLE PLATE GOVERNOR CONTROL LINKAGE GOVERNOR SPRING BOVERNOR SENSITIVITY ADJUSTMENT LOW SPEED STOP ADJUSTMENT GOVERNOR SHAFT YOKE FIGURE 9 GOVERNOR ADJUSTMENTS POLYURETHANE PRE CLEANER ELEMENT BREATHER HOSE AIR INTAKE TUBE AIR CLEANER caution air cleaner becomes too dirty engine will not receive sufficient air to run properly Symptoms Loss of power flooding hard to start and overheating This engine is equipped with a paper element and a polyu
51. sely omitted from this Parts Catalog due to the confusion resulting from fluctuating costs import duties sales taxes exchange rates etc For current parts prices consult your Onan Dealer Distributor or Parts and Service Center CYLINDER BLOCK GROUP 410 5 1012 354 5 MMM 3914 Jauyoue 30 REF PART QTY PART No USED DESCRIPTION NO NO USED DESCRIPTION 110 1975 Block Assembly Cylinder 22 NUT Includes Parts Marked T 10 0445 18 Cylinder Head Hex 2 123 1174 Spring Breather Valve 5 16 24 3 123 1175 Valve Breather 866 0001 2 Valve Cover Acorn 4 123 1173 Baffle Breather 174 20 Spec A Through 5 WASHER FLAT 23 110 0893 4 Retainer Valve Spring 526 0018 Breather Valve 1 4 Steel 24 TAPPET VALVE 526 0063 2 Valve Compartment Cover 115 0006 4 Standard 174 Copper 115 0006 01 4 001 Oversize 526 0122 18 Cylinder Head Screws 1 15 0006 02 4 002 Oversize 5 16 Steel 115 0006 05 4 005 Oversize 6 COVER VALVE COMPARTMENT 25 850 0050 5 TWasher Lock 3 8 Rear 110 1878 Cover with Opening for Bearing Plate Breather Tube L H 26 120 0706 TTube Crankcase Oil Oo 110 1879 Cover without Opening for 27 VALVE O Breather Tube R H 110 1808 2 Intake 7 110 1921 3 Gasket Valve Cover 110 1809 2 Exhaust N 8 517 0048 TPlug Camshaft Expansion 28 INSERT VALVE SEAT EXHAUST 9 STUD 10
52. valve clearance only when engine is at ambient temperature Proceed as follows 1 Remove ignition key from tractor to prevent acci dental starting Remove all parts necessary to gain access to valve tappets Remove spark plugs to ease the task of turning the engine over by hand Use the engine flywheel to turn the engine over slowly by hand until the left hand intake valve opens and closes Continue turning the flywheel until the TC mark is on the top and lined up with the TC mark on the gear cover Both valves should be closed This should place the left hand piston at the top of its compression stroke the position it must be in to get proper valve adjustment for the left cylinder For the intake valve 007 thickness gauge should pass freely between valve stem and tappet a thicker 009 gauge should not Figure 24 For the exhaust valve a 012 thickness gauge should pass freely between the valve stem and the tappet a thicker 014 gauge should not To correct the valve clearance use a 7 16 open end wrench to turn the adjusting screw to obtain the correct clearance The screw is self locking and will stay where it is set 9 16 open end wrench is required to hold the tappet while turning the adjusting screw To adjust valves on the right hand cylinder turn engine one complete revolution and again line up mark on the flywheel and the TC mark on the gear cover Then follow adjustment procedure given
53. y When installing the governor cup tilt the engine so the gear is up put the flyballs in place equally spaced and install the cup and snap ring on the center pin The camshaft center pin extends out 3 47 from the end of the camshaft This distance provides an in and out travel distance of 7 32 for the governor cup as illustrated Hold the cup against the flyballs when measuring If the distance is less the engine will race especially at no load remove the center pin and press in a new pin or grind off the hub of the cup as required The camshaft center pin cannot be pulled outward or removed without damage If the center pin extends out too far the cup will not hold the flyballs properly WHEN GOVERNOR 15 PROPERLY ASSEMBLED THE DIMENSION SHOWN ON DRAWING WILL BE AS INDICATED 7 32 CENTER PIN SNAP RING FIGURE 27 GOVERNOR CUP DETAIL another free manual from www searstractormanuals com E CRANKSHAFT GEAR x X GEAR 4 PULLER 8 GEAR PULLER RING xt Wig THESE MARKS MUST COINCIDE WHEN IN STALLING TIMING GEARS FIGURE 28 TIMING GEAR REMOVAL AND INSTALLATION TIMING GEARS If replacement of either the crankshaft gear or the camshaft gear becomes necessary always install both gears new To remove the crankshaft gear first remove the snap ting and retainer washer then attach the gear pulling ring using two No 10 32 screws Figure 28 Tighten the

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