You may have a 2 stroke, but sounds like you have never had a CR500!
Valves are a once a year maybe twice thing. I personally love wrenching on the bikes, almost as much as riding so it's of no concern to me. While your halfway through a race mixing gas, changing plugs or rings or that clutch you gotta ride the snot out of I'll wave as I pass by w/ 4000 miles on the same topend going strong.
BTW- you didn't happend to catch my sarcasm in the last post. I have a two stroke.
That was the best, most reliable bike going. You could get 2 seasons out of a piston and rings!