Having burned more than a few valves on off road dirt bikes... I can say that having poor compression... Is a bit too late in the game. By that time the valve seats or heads are toast, it's too late to adjust them. Keep that air cleaner clean! All of my 4 22R Toyotas and 5 Honda motorcycles are overhead cam, screw and locknut adjustable, by the owner. No shims . So far it seems that no auto shop has any real world experience in doing a shim adjustment for the V6 engine. Search until you find one. You shouldn't have to pull more than the cylinder heads, at most.
