Ok, so since my yz is all tore apart because 5th gear blew, I'm going to rebuild the valves. I don't think I need replace the piston. The previous owner said it was done about 10 hours before I bought the bike and it still looks good. I want to keep the cost down because I'm laid off right now so don't have alot of money coming in. Sorry if the questions are a little noobish, but this is my first 4 stroke. My questions are: 1. What parts do I need to replace to rebuild the head? 2. The valve clearance was just below minimum when I checked it when it was together. Can I get away with keeping the same valves and putting in smaller shims? 3. How do you get the valve seats out of the head? I've got one valve out but the stem and seat is stuck in the head.