Just giving yammie a plug. Just checked my valves on my 04 Yz450f and i'm not sure but im gonna guess it has around 100+ hours on it with no problems. The valves are still at the same clearance when i checked 25 hours ago. Time to do the timing chain though atleast i think it is? I've never jetted my bike either and it doesn't have the infamous bog that everyone else talks about. Good stuff keep cranking em out yamaha. After hearing all the horror stories i was leary going to a 4 stroker, now i'm not.