Summary Of Engine Specifications

(Fitting and Adjusting)

CYLINDER: Standard bore—O.H.V. Engine: 61"—3.3125"; 74"—3.4375". Side Valve Engine: 74"—3.3125"; 80"—3.422".

PISTON CLEARANCE IN CYLINDER: .001" to .002", measuring piston at bottom of skirt front to rear. Piston shapes to cylinder and acquires more clearance alter short time in service. Measure cylinder about W bom top of bore, front to rear. Warning: This fitting clearance applies only to genuine Harley-Davidson taper-cam ground piston, which is smaller at top -of skirt underneath lower ring, than at bottom of skirt. This clearance (.001" to .002") is not sufficient for straight-cam -ground piston obtained from some other source.

PISTON-CYLINDER HEAD CLEARANCE: Side Valve Engine—1/16" to 3/32" with piston at top center. ,

PISTON PIN IN PISTON: Light hand press fit.

PISTON PIN IN CONNECTING ROD UPPER BUSHING: .0008" to .0012" loose.

PISTON RING SIDE CLEARANCE IN GROOVES: .004".

CONNECTING ROD LOWER END BEARING: .001" to .0012" loose.

CONNECTING ROD LOWER END SIDE PLAY: Forked rod must have .006" to .010" play between flywheels. Roller and retainer assembly must be narrower, but not more than .010" narrower, than forked rod.

PINION GEAR SHAFT: .0008" to .0012" loose in roller bearing and .0005" to .0012" loose in timing gear case cover bushing. Note: When new cover bushing is installed, oil transfer hole in bushing must be located as follows: O.H.V. Engine—oil transfer hole in bushing must line up with drilled oil passage in gear case cover; Side Valve Engine—oil transfer hole in bushing must be upward and 30° ahead (toward front of engine) of vertical center line.

SPROCKET SHAFT: .0005" to .001" loose in roller bearing; .007" to .009" loose in oil retaining bushing.

FLYWHEEL ASSEMBLY: .012" to .014" endplay in crankcase.

CAM GEARS: OJi.V. Engine—.001" to .0015" clearance in crankcase and gear case cover bushings; free to .005" endplay; Side Valve Engine—.0005" to .001" clearance in crankcase and gear case cover bushings; free to .007" endplay.

INTERMEDIATE GEARS: .001" to .0015" loose on studs.

VALVE STEM-VALVE GUIDE CLEARANCE: O.H.V. Engine— .004" to .006"; Side Valve Engine—.003" to .0055".

TAPPET GUIDES: .0005" to .001" press fit in crankcase.

VALVE TAPPET—TAPPET GUIDE CLEARANCE: O.H.V. Engine—.0008" to .0017"; Side Valve Engine—.0005" to .001".

ROCKER ARM FIT ON SHAFT: O.H.V. Engine—.0005" to .0015" loose—.007" to .016" endplay.

OIL PUMP DRIVE SHAFT: OJI.V. Engine—.0008" to .0012" loose in crankcase bushing.

TAPPET CLEARANCE: Engine Cold: O.H.V. Engine—push rods just noticeable play or shake, and can be turned freely with finger tips, completely around, without any trace of bind. Side Valve Engine—intake .004" to .005"; exhaust .007" to .008".

CIRCUIT BREAKER POINTS: .022" gap with breaker lever fibre on highest point of cam.

IGNITION TIMING: O.H.V. Engine—7/16" before top dead center; Side Valve Engine—11/32" before top dead center; time according to flywheel mark. Page 81 or 82, or by piston position, Page 86.

CRANKCASE BREATHER TIMING: O.H.V. Engine—breather valve gear engaged with marks in alignment (see Illus. 64). Side Valve Engine—See Page 70.

VALVE TIMING: Time according to gear marks (see Page 78). Tappets to be adjusted first.

CHECKING VALVE TIMING: All OJI.V. Engines—adjust all valve tappets temporarily to .004" clearance. Turn engine in direction it runs until valve being checked is open .001" before measuring piston position. After timing has been checked, valve tappets must be readjusted to the correct clearance, see "Adjusting Valve Tappets," Page 22. 61" OJI.V. Engine—intake valve opens when piston is 19/64" to 25/64" before top dead center and closes when piston is 29/32" to 1-3/32" after bottom dead center. Exhaust valve opens when piston is 23/32" to 29/32" before bottom dead center and closes when piston is 19/64" to 25/64" after top dead center.

74" O.H.V. Engine—intake valve opens when piston is 23/64" to 29/64" before top dead center and closes when piston is 1-1/64" to 1-13/64" after bottom dead center. Exhaust valve opens when piston is 13/16" to 1" before bottom dead center and closes when piston is 23/64" to 29/64" after top dead center.

Side Valve Engine—intake and exhaust valve tappets adjusted to running clearance—intake valve tappets .004" to .005"; exhaust valve tappets .007" to .008". Turn engine in direction it runs until valve being checked is just starting to open before measuring piston position.

Intake valve opens when piston is 9/32" to 13/32" before top dead center and closes when piston is 7/s" to lVa" after bottom dead center. Exhaust valve opens when piston is 5/a" to %" before bottom dead center and closes when piston is 'A" to %" after top dead center.

OIL PUMP ADJUSTMENT: Normal setting—O.H.V. Models—end of presssure regulating valve adjusting screw %" below end of valve chamber. Side Valve Models—1940 and earlier Models—pressure regulating valve adjusting screw nine complete turns open from closed position, 1941 and later Models—end of pressure regulating valve adjusting screw %" below top of pump body. See "Adjusting Oil Feed Pump," Page 28.

FRONT CHAIN OILER ADJUSTMENT: Initial factory setting—O.H.V. Models—adjusted with the required washers under adjusting screw head to hold screw point 1 full turn off its seat. Make further adjustments as needed to meet actual service requirements. See "Lubricating Front Chain," Page 12. Side Valve Models—adjusted with the required washers under adjusting screw head to hold screw point l'/s turns off its seat. Make further adjustments as needed to meet actual service requirements. See "Lubricating Front Chain," Page 12.

REAR CHAIN OILER ADJUSTMENT: (Installed on a few motorcycles): Initial factory setting—adjusted with the required washers under adjusting screw head to hold screw point V2 turn off its seat. Make further adjustments as needed to meet actual service requirements. See "Lubricating Rear Chain," Page 14.

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