CHAPTER 3. ENGINE OVERHAUL

t aaaajgggggBSaSttSPmSSCHAPTER 3. ENGINE OVERHAUL3-1.3-2.3-3.3-4.3-5.REMOVALA. Preparation for RemovalB. ExhaustC. CarburetorD. RemovalDISASSEMBLYA. Reed Valve AssemblyB. Main StandC. Kick Crank (Kick Starter)D. Drive Shaft (Rear Arm Comp.)E. MagnetoF. Cylinder Head and CylinderG. Piston Pin and PistonH. Crankcase Cover, RightI. Clutch Assembly and Primary Drive GearJ. Kick Shaft Assembly, Drive Gear and Kick Pinion GearK. TransmissionL CrankcaseM. Crankshaft.INSPECTION AND REPAIRA. Cylinder HeadB. CylinderC. Piston Pin and BearingD. PistonE. Piston RingsF. Autolube PumpG. ClutchH. Kick StarterI. TransmissionJ. CrankshaftK. Bearing and Oil SealsL. CrankcaseENGINE ASSEMBLING AND ADJUSTMENTA. Crankshaft InstallationB. CrankcaseC. Transmission InstallationD. Kick Starter AssemblyE. Primary Drive Gear and Clutch AssemblyF. Crankcase Cover (Right)G. PistonH. CylinderI. Cylinder -123-13

"Wt*;tf57v e'"d'J": CHAPTER 3. ENGINE OVERHAUL: :3-1.' fe' . ,:'; ' wmZm Vi'REMOVALA. Preparation for RemovalWiw1. Always clean engine before removal.Do not begin work until all proper toolsare available. As parts are removed,clean them and place them in trays inorder1 of disassembly.2. Start the engine and warm it for a fewminutes. Turn off and drain transmissionoil. Before begining of the servicing,fully cool the engine down.affiBBBMHiftm2. Disconnect the magneto lead wire.3. Remove the rear fender.4. Remove the rear brake cable from shaftdrive housing.5. Remove the nut and rear wheel fromshaft drive housing.B. Exhaust1.2.3.4.RemoveRemoveRemoveRemovefootrest protectors. (R.L)side covers. (R.L)sparkplug cap.the footrest from the frame.NOTE:Immediately when the rear wheel is removedfrom the housing, place a wooden frame orblock under the rear carrier to keep the machine upright.6. Remove air cleaner joint and clip, aircleaner case assembly.5. Remove exhaust pipe assembly.1. Air cleaner case2. Air cleaner joint3. Clip7. Remove the delivery pipe from carburetor.8. Remove the pump cover (1) and pumpcable and oil pipe.C. Carburetor1. Remove thebracket.ignitioncoilandNOTE:Do not leave the oil pipe disconnected fromthe oil pump, or oil will flow out of the oiltank. It is advisable to plug the open pipe endwith a proper size screw.coil3-2

B. Main StandRemove main stand and bracket from engine.9. Remove the carburetor.D. Removal1. Remove rear shock absorber holdingbolt from shaft drive.C. Kick Crank (Kick Starter)Remove kick crank securing bolt and kickcrank.D. Drive Shaft (Rear Arm Comp.)Remove rear arm comp. from engine.2. Remove the engine mounting bolt andremove engine from front side of frame.3-2. DISASSEMBLYE. Magneto1. Remove left crankcase cover screw andcover.2. Remove the flywheel securing nut. (useFlywheel holding tool)A. Reed Valve AssemblyRemove manifold, reed valve assembly holding screws and reed valve assembly.1.2.3.4.5.6.7.8.9.10.Reed valve assemblyReed valveReed valve stopperPanhead screwSpring washerReed valve plateValve seat packing 1Valve seat packing 2ManifoldPanhead screw1. Flywheel holding tool3-3

nilII3. Install flywheel puller on flywheel andtighten it.NOTE:Loosen spark plug before loosening cylinderhead.NOTE:The puller body has lefthand thread.Cylinder headCylinder head gasketSparkplugCylinder body5.6.7.8.Cylinder gasketStud boltPlate washerHexagon nutPiston Pin and PistonRemove piston pin clip from piston.1. Flywheel pullerNOTE:Before removing the piston pin clip, coverthe crankcase with a clean rag so you willnot accidentally drop the clip into the crankcase.10.11.12.13.14.15.16.17.18.I 'T " '1.2.3.4.C.D.I, magnet assemblyRotor assemblyMagnet baseSource coilPulser assemblyLighting coilLead wire assemblyClampPan head screwH ,-I4. While holding puller body, tighten pushbolt. This will pull flywheel off thetapered end of the crankshaft.1.2.3.4.5.6.7.8.9.ISpring washerPaahead screwSpring washerPanhead screwSpring washerPanhead screwEarth 1 terminalEarth 2 terminalFlathead screw2. Push piston pin from opposite side, thenpull out. Protect pin with rag.NOTE:Before removing pistongroove and pin hole area.F. Cylinder Head and CylinderRemove cylinder head holding nuts, cylinderhead gasket and cylinder head. Loosen cylinder head holding nuts 1/4 turn each, thenremove nut.pin, deburrclipH. Crankcase Cover, RightRemove right crankcase cover screws andcover.3-4

ilUUI.Clutch Assembly and Primary DriveGear1. Remove circlip and clutch housing.1.23.4.567.890. *.»Primary drive gearAbsorber 1Absorber 2Thrust plateSpacerCollarStraight keyPlate washerHexagon nutCirclip11.12.13.14.15.16.17.18.19.Plate washerClutch carrier assemblyClutch weight shaftSpringWasherCirclipClutch weight damperClutch housing comp.CirclipJ. Kick Shaft Assembly. Drive Gear andKick Pinion Gear1. Remove the circlip, drive gear and kickpinion gear.2. Remove the kick shaft assembly.Remove the primary drive gear. Feed arolled-up rag between the tooth of theprimary drive gear and primary drivengear to lock them and loosen theprimary drive gear lock nut.K. Transmission3. Remove clutch carrier assembly.1.2.3.4.Main axle comp.Pinion shimCover plateStopper5. Bolt7.8.9.10.11.Thrust shimBearingDistance collarScrewOil seal6. Middle driven pinion1. Remove the cover plate from the rightside case and pull out the main axle.Don't forget to remove the pinion shimfrom inside of the case.3-5

fcSPSML. Crankcase1. Working in a crisscross pattern, looseneach screw 1/4 turn. Remove screwsafter all are loosened.' ' ' ifX% *ft:i2. To remove the oil seal, it is advisable touse long-nose pliers. Insert the longnose pliers into a soft area of the oilseal, pinch it and pry it out.2. As illustrated below, remove the crankcase-right by tapping it with a softfaced hammer.r-CAUTION:Place a wooden piece on the case toprotect it against scratching.The screw has a mark "OPEN -*" on itshead. Turn it in the direction of the arrow to remove.oVOycC?" ———iv \\aT\Wti \ )Efpv2/"-0 M. CrankshaftRemove crankshaft assembly with the Crankcase Separating Tool.Use two hexagon bolts (P/No.90890-01305).V *-' .v!'.f f if.:1. Screw2. Hexagon wrench1. Crankcase separating tool3. Remove the distance collar, bearing,driven pinion, and thrust shim form therebore to next over-size.3-6

L » » J « U W J M I MmifaKg aatacBg igPaffi i'3-3. INSPECTION AND REPAIRV. Cylinder Head1. Remove spark plug.2. Using a rounded scraper, remove carbon deposits from combustion chamber.Take care to avoid damaging spark plugthreads. Do not use a sharp instrument.Avoid scratching the combustion chamber surface.s m3. Place on a surface plate. There shouldbe no warpage. Correct by re-surfacingas follows:Place 400 600 grit wet sandpaperon surface plate and re-surface head using a figure-eight sanding pattern.Rotate head several times to avoid removing too much material from oneside.B. Cylinder1. Hone cylinder bore using a hone withfine stones. Hone no more than requiredto remove all wear marks.2. Using a Cylinder Gauge set to standardbore size, measure the cylinder. Measure front-to-rear and side-to-side attop, center and bottom just above exhaust port. Compare minimum andmaximum measurements. If over tolerance and not correctable by honing,rebore to next over-size.C. Piston Pin and BearingApply a light film of oil to pin and bearingsurfaces. Install in connecting rod small end.Check for play. There should be no noticeablevertical play. If play exists, check connectingrod small end for wear. (Replace pin andbearing or all as required.)D. Piston1. Remove carbon deposit from ringgrooves using old piston ring as shown.2. Using an outside micrometer, measurepiston diameter. The piston is camground and tapered. The only measuringpoint is at right angles to the piston pinholes about 5 mm (0.20 in) from bottom of piston. Compare piston diameterto cylinder bore measurements.Max. allowable taper (d — a):0.05 mm (0.0020 in)Max. allowable out-of-round( B - A o r A - B):0.01 mm (0.0004 in)Wear limit: 40.10 mm (1.579 in)(at "a" position)3-7

: ;-:-Piston maximum diameter (as shownbelow) subtracted from minimumcylinder diameter (d —B) gives pistonclearance. If beyond tolerance, honecylinder to tolerance or re-bore to nextover-size and fit over-size piston.3. With rings installed in grooves, insertfeeler gauge between ring and groove. Ifbeyond tolerance, replace ring and/orpiston as required. ivifflSMinimumMaximum0.03 mm(0.0012 in)0.05 mm(0.0020 in)5 mm(0.20 in) Vti,-m L H ;r ;:.11,"-Piston clearanceMinimumMaximum0.035 mm(0.0014 in)0.047 mm(0.0019 in)10.07 mm(0.0030 in)Maximum wear limitF. Autolube pump1. Troubleshooting and repaira. Wear or an internal malfunction maycause pump output to vary from thefactory setting. This situation is, however, extremely rare. If output is suspect, check the following:1) Obstructions in delivery line to pumpor from pump to carburetor.2) Worn or damaged pump body seal orcrankcase cover seal.3) Improperly installed or routed oildelivery line(s).4) Loose fitting(s) allowing air entry topump and/or engine.b. If all inspection show no obvious problems ad output is still suspect, connectthe delivery line from the pump to agraduated container (cc). Keep the delivery line short. Remove spark plug.Open throttle to full open position. Operate kick starter continuously andcount the oil pump plunger strokes. Ifoutput is not to specification, replacepump assembly.E. Piston Rings1 Check rings for scoring. If any severescratches are noticed, replace ring set.Insert each ring into cylinder. Pushdown approximately 20 mm (0.79 in)using piston crown to maintain rightagle to bore. Measure installed end gap.If beyond to tolerance, replace set.Ring end gap (installed)— TopIumWy0*p. 'f.Ring groove clearanceTop/SecondSecondMinimumMaximum0.15 mm(0.006 in)0.15 mm(0.006 in)0.35 mm(0.014 in)0.35 mm(0.014 in)Minimum throttlePump outputfor 200 strokes(100 cycles)3-8:i t l f '. '.7-.l l t f J i Wm?.,Pr& r*'v* —-- 1Maximum throttle0.91 1.06 cc0.19 0.24 cc(0.006 0.008 oz) (0.031 0.036 oz)

2.ReassemblyAlways install a new pump case O-ring.Wm 1.2.3.4.5.6.7.8.9.Oil pump assemblyOil sealO-ringDelivery pipeClipGasketBind screwAdjusting plateHexagon nut10.11.12.13.14.15.16.17.18.H. Kick StarterCheck the ratchet teeth on the kick gearand drive gear. The matching edgesshould fit flush against each other. Ifthere is severe rounding off, replace asa set. (Kick gear and drive gear)Union boltWorm wheel gearPinCirclipPan head screwPanhead screwCover 1Cover 2Panhead tapping screwG. Clutch1. Measure the clutch shoes lining tness. If their minimum thickness exceeds tolerance, replace.If any sign of seizure are found, replacethem.I. Transmission1. Main axle assembly and middle drivenpinion assemblyUsing a dial gauge, measure the amountof deflection of the axle. If exceeds thelimit, replace the mian axle assemblyand middle driven pinion assembly atthe same time.Clutch shoe lining thickness:S.T.D.: 1.0 mm (0.040 in)Wear limit: 0.7 mm (0.03 in)Delection limit: 0.25 mm (0.010 in)2. Measure each clutch shoes spring. Ifbeyond tolerance, replace.—— Clutch shoe springfree lengthNewLimit34.5 mm(1.36 in)35.5 mm(1.39 in) 43-9