I have an '04 yz 450 and LOVE IT!!!! I've put a lot of time and money into mods on it - PWR low boy radiators, Storm Cycle link, Factory Connection revalve, Triple clamps, exhaust and so on. I keep reading about how rebuilds consist of new case halves and new cylinders and new heads and how it's about $2000. I would think that with proper maintenance, oil and filter changes, along with top end and valve jobs the cylinders and heads and cases should last a long time. I realize if you let your motor go bad things happen but are the new thumpers destined to have the motors "grenade" and need to be completely replaced? Acording to MXA nothing over about 5 years old will last. I would like to keep my '04 and someday race it in a vintage class. Is this realistic?