valve tappet clearence

[mat4]

I have been told that through use the valve tappet gap gets smaller as the valve beds deeper into its seat, I always thought that with wear the clearence would increase not decrease, which is true, anyone know?

[SteveD CB500K0]

Wear causes the valve clearance to increase. So they rattle.

On DOHC bikes with shim/bucket arrangement, the opposite is true. As the shim wears the valve tightens. A nice quiet engine is not necessarily a good thing!  My Triumph Sprint ST came back from it's 24k service sounding all tappety (is there such a word?) as all 12 valves were tight.