1997 RM250 problem with valves

I did a top end on my RM250 last weekend. When I took out the piston it was damaged on one side. At the main exhaust port in the bottom of the cylinder the valve is actually sticking into the chamber, so the piston was hitting it.

The person who had it prior to the guy I bought it from apparently adjusted the power valves (the same as exhaust valves?) in order to de-tune the engine and take some power out of it. I can't see how to adjust these, though.

Is this a sign that the valves are just worn and need to be replaced or is there a way to adjust them to back it out of the cylinder? Thanks!

Anyone? I am getting anxious to just pull everything apart again at this point. No good can come of that :)

Ok. Well I just ordered another gasket kit so I can tear it down next week and check it as I adjust them. I am hoping I don't have to replace the exhaust or governor assy. Bah. Thanks for the replies.