The initial valve clearance adjustment should be made after the first 100 to 125 service hours of operation. Thereafter, the clearance should be checked and adjusted if necessary after every 500 service hour interval.
The valve clearance adjustment should be made on a cold engine or on an engine that has been shut down long enough for the heat in the engine to dissipate. The compression release lever must be in RUN position whenever valve clearance and compression release clearance is being checked or adjusted.
To Adjust: With the camshaft cover removed, proceed as follows:
- 1. Rotate the crankshaft in the direction of engine rotation until the valve to be adjusted is closed. The cam (1) over the valve to be adjusted will indicate a closed valve when the cam lobe is in any location within the 180° arc (2).
VALVE CLEARANCE ADJUSTMENT
1-Cam. 2-Valve is closed when cam lobe is in any location within this 180° arc. 3-This clearance on a cold engine should be, exhaust valve .030 inch (.76 mm.), inlet valve .018 inch (.46 mm.). 4-Cross point (Phillips) screwdriver. 5-Cam follower. 6-Diagonal hole in follower.
- 2. Turn the cam follower (5) on the valve to be adjusted until the diagonal hole (6) in the follower is toward the center of the engine.
- 3. With a cross point (Phillips) screwdriver (4) in the diagonal hole (6) in the cam follower, turn the screwdriver clockwise to increase or counterclockwise to decrease the valve clearance at (3) enough to allow a thickness gauge of the correct thickness to be passed between the cam follower (5) and the cam (1). Valve clearance on a cold engine should be .030 inch (.76 mm.) for exhaust valves and .018 inch (.46 mm.) for inlet valves. An engine that is close to operating temperature should have a clearance of .025 (.64 mm) for exhaust valves and .015 inch (.38 mm.) for inlet valves.
Compression Release Adjustment: Compression release clearance should be adjusted whenever inlet valves have been adjusted. The inlet valve under the compression release lever (3) to be adjusted must be closed. To make the adjustment proceed as follows:
- 1. Loosen the locknut (1).
- 2. Turn the adjusting screw (2) and adjust the clearance (5) to allow a thickness gauge of .030 inch (.76 mm.) to pass between the compression release lever (3) and the cam follower (4).
COMPRESSION RELEASE ADJUSTMENT
1-Locknut. 2-Adjusting screw. 3-Compression release lever. 4-Cam follower. 5-Compression release clearance .030 inch (.76 mm.).
- 3. Tighten the locknut (1) and recheck the clearance.
Valve Rotation: Whenever the engine is running the valves slowly rotate. Valve rotation decreases carbon build up and uneven wear, thereby increasing the life of the valves. The followers also slowly rotate when the engine is running, but cam follower rotation does not necessarily indicate valve rotation. If it is suspected that a valve is not rotating see your AVSpare dealer.