Figure 4-16. Adjusting Valve Tappet Clearance

TM 10-3930-644-14&P

2. Remove valve tappet cover from left side of

engine.

This includes disconnecting and

removing fuel pump with front cover.

3. Remove the spark plug from No. 1 cylinder.

4. Place thumb over the spark plug opening and

slowly crank the engine until an outward

pressure can be felt. Pressure indicates No. 1

piston is moving toward top dead center of the

compression stroke. Continue cranking until the

timing mark on the flywheel is in center of

opening in flywheel housing. Both valves are

then closed on the compression stroke of No. 1

cylinder.

5. Use two thin open end wrenches when making

adjustment. The lower wrench is used to raise

Figure 4-16. Adjusting Valve Tappet Clearance

or lower the tappet adjusting screw after the

locknut has been loosened. Never attempt to

valves in succession, according to the firing

adjust without first loosening the adjusting screw

order of the engine: 1-3-4-2.

locknut. The feeler gauge should pass between

the valve stem and tappet adjusting screw with a

7. Replace the valve tappet cover and other

slight drag when the valve lash is properly

removed parts. Make sure cover makes an oil-

adjusted.

tight seal with the crankcase. Replace gasket.

6. Crank the engine one-half revolution at a time,

8. Replace the spark plug and coil wire.

and check the clearance of each valve; adjust if

necessary. Do this on each set of cylinder

R-104-1

3-12