Does the throttle click when the engine is idling? What's going on here?

When the engine is idling, there is a continuous rhythmic "click, click" knocking sound between the end of the valve stem and its driving part, which increases with the increase of speed, and the sound remains unchanged when the engine temperature changes or shuts down.

The main reasons are as follows: a. The adjusted valve clearance has changed (the locking is not firm, the valve stem and transmission part are worn), and the valve adjustment is not good. B the valve adjusting screw is worn, the locking nut is loose, and the valve clearance is too large or inconsistent. C. The valve spring retainer ring is worn out of the groove, and the valve stem and guide tube are excessively worn.

Treatment: Re-adjust the valve clearance. If the lock nut on the adjusting screw is loose, lock it and replace the seriously worn parts.