Determining Correct Cam Gear End Play

Before final reassembly of the timing gears, correct cam gear end play must be established. Temporarily position the two cam gear plates (11, Fig. 3D-11), less shims, in the gearcase compartment. Position against crankcase with beveled side of holes for cam shaft facing outward toward cams. Install cam gears. Assemble the case cover with a dry gasket and securely tighten in place (less generator bolts).

Figure 3D-15. Installing Tool for Line-Reaming Cam Gear Timer Shaft Bushing

Turn the engine over until the number one cam gear lobe is facing up as indicated through the tappet guide hole in the crankcase. Using a long shank screwdriver, pry the cam gear towards the case cover. With a feeler gauge, measure the clearance (end play) between the cam shaft shoulder and the gear plate. Repeat this operation for remainder of cam gears.

Correct cam gear end play is .001 to .006 in. If end play exceeds the maximum specification, add necessary number of .005 or .007 in. thickness steel shims to obtain recommended running clearance. After adding shims, turn engine over to be sure cam gears turn freely.


The breather must be retimed if disengaged from mating oil pump drive gear (spiral gear) on pinion shaft. To check breather timing proceed as follows:

Flywheel timing mark (1) should be exactly in center of timing inspection hole in left side of crankcase.

Oil pump drive gear (spiral gear) (2) is located on splined shaft behind pinion gear (3). Spiral gear is a slip fit on splines. A mark is cut on one side of spiral gear, which should face outward against pinion gear when assembled to shaft.

Assemble spiral gear against shoulder on pinion shaft engaging breather sleeve gear tooth which will register timing hole in breather sleeve (4) in center of slot in breather bushing as shown.

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