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I have a Briggs & Stratton mower with engine 12H882-3173-E1. Is there any valve adjustment that can be done on this type engine (other than grinding down the end of the valve)? I can access the valves under the breather (as shown below) if I wish to remove them, but I don't see any way to adjust them. I see (from parts diagrams) there are tappets located inside the engine, but not clear if there is anything adjustable. I don't know if any adjustment is warranted, I'm simply trying to touch on all possible maintenance points. Thanks for any advice.

Nothing adjustable outside of grinding the stem of the valve to reset the clearance

Thank you!

Hmmm, I think we are in the same boat !
My old 8HP rider refuses to die, so, I must run higher RPM, which causes old-valve-rattle.
The solution - try adding a little two-cycle oil to your gas. Just a 'tad'.
If it smokes, that's too much.
Note: this was written 3 years ago,,, its still running !