: Rotate the engine manually to Top Dead Center (TDC) for the cylinder you are adjusting. This ensures the valves are fully closed and the tappet is on the base circle of the cam lobe.
A is the sleeve or housing that keeps the tappet moving in a perfectly straight line. DOC HARLEY: TAPPET GUIDE ALIGNMENT TOOL USES
: Remove the valve (rocker) cover. Always check your specific engine's service manual for the correct clearance specifications.
Turn the adjuster screw with a screwdriver until the correct clearance is reached.
: Insert a feeler gauge between the tappet and the valve stem (or rocker arm). The gauge should have a "slight drag" when pulled through. Adjust : Loosen the lock nut using a spanner.