TM 5-3895-346-14
CAMSHAFT GEARS
ENGINE OVERHAUL
CAMSHAFT AND BAIANCE SHAFT GEARS
The camshaft and balance. shaft gears on an in-line engine are located at the flywheel end of the engine and
mesh with each other and run at the same speed as the crankshaft.
Sixnce the camshaft and balance shaft gears on in-line engines must be in time with each other, timing marks
are stamped on the rim of each gear. Also, since these two gears as a unit must be in time with the crankshaft,
timing marks are located on the idler and crankshaft gears (refer to Gear Train and Timing).
Each gear is keyed to its respective shaft and held securely against the shoulder on the shaft by a nut. A gear
nut retainer, with a double-hexagon hole in the center, fits over the nut on some engines. The retainer is
attached to the gear by bolts threaded into tapped holes in the gear.
On the four-cylinder in-line engines, external weights are attached to the rear face of each gear. The weights
are important in maintaining perfect engine balance.
When new service gears are used on an in-line engine, the external weights on the old gears must be
transferred to the new gears. If the weights are transferred to new gears, tighten the bolts to 45-50 lb ft (61-68
Nm) torque.
Remove Camshaft and Balance Shaft Gears
1. Remove the camshaft and the balance shaft from the engine as outlined in Camshaft and Bearings.
2. Place the camshaft and gear assembly in an arbor press with the gear suitably supported as shown in
Fig. 1.
3. Place a woodblock under the lower end of the camshaft so the threads will not be damaged when the
shaft is pressed from the gear.
Figure 1. Removing Camshaft Gear
4. Place a short piece of 3/4-inch O.D. brass rod on the end of the camshaft and press the camshaft out
of the camshaft gear.
5. Remove the thrust washer, woodruff key, and spacer from the camshaft.
6. Remove the gear from the balance shaft in a similar manner.
Inspection
Clean the gears with fuel oil and dry them with compressed air. Then examine the gear teeth for evidence of
scoring, pitting, and wear. Replace the gears if necessary.
Examine both faces of the camshaft and balance shaft thrust washer and, if either face is worn or scored,
replace the washer. Also examine the surface on the camshaft and balance shaft which the thrust washer
contacts. If this surface is scratched, but not severely scored, smooth it up with a fine oil stone.
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