Well, this is my second CRF450R. Previously I rode an 04. I had to adjust the valves once on my previous CRF then I sold it, I probably had 80-100 hours on it but did not have an hour meter. I did install an hour meter on my 07 when it was new. I have had to adjust the valve 2-3 times on the 07 and now I am done, one of my intake valves has no clearance with the smallest shim (98.5 hours). I ALWAYS change my oil and clean my air filter (I own four air filters and I rotate). I don't ride on the rev limiter and am a novice/intermediate rider. I used to only trail ride but this year I raced MX, probably 12-14 races. I have no doubt that the valve issue is not maintenance or rider related. I know that this is probably not news to some but I also know others have their differing opinions (from what I have read). Now I need to make a decision and I am thinking about a new head from Big Bore Thumpers. I only have one intake valve that is done (the other is not too far behind) but I have never had to adjust the exhaust valves. Due to cost, I am also considering just replacing just the intake valves/springs. Either way I am going SS, I don't care if I do loose .05hp (or whatever), I would rather not keep working on this SOB. What about a piston/rings? Do you usually find that you need a new piston at 100hrs? I am planning to pull this thing apart this week but for cost purposes I am trying to figure how much all of this is going to cost me. I am normally the kind of guy to spend more and be happy. I have read that the exhaust valves are already SS and that I would not need to worry about them? Intake Valves Only (Cheaper Route) $140 intake valves/springs from Big Bore $80 Labor $75 Gasket Kit $60 shipping $250 Total Complete Head (More Expensive Route) $549 Complete Head from Big Bore $30 Shipping $300 Piston & Ring $75 Gasket Kit $955 Total What am I missing or what do you recommend?