A tappet is most commonly a component in an internal combustion engine which converts the rotating motion of the camshaft into linear motion of the valves, either directly or indirectly.
source/image(PrtSc): Bishnu Darnal
Before adjusting tappets you should always refer to the manufacturer’s instructions for the correct tappet gap clearance setting, and how to position the tappet for measurement. This video explains tappet clearance and its purpose both in a theoretical and practical way. Watch the video from Bishnu Darnal for more info:
Once the locknut is disengaged; tappet is free to move up and down. Adjust the tappet clearance by adjusting the position of the tappet. To ensure the correct clearance setting it is a common practice to place the filler gauge of the desired dimension in the clearance area during adjustments.
Make sure you can slide the filler gauge smoothly once it is set; Too easy to pass is a clear indication of high clearance. This is sometimes hard to judge making it a job of skill and experience.A small turn will ensure movement up to one-hundredth of a millimeter. Clearance should be set when the engine is cold and the cam follower is off the cam peak.// Bishnu Darnal