snopro-54 said:
How often should my top end be rebuilt on my CRF 450?
Honda provides a very useful
and accurate service interval guide in the factory service manual. It's very useful for answering these questions.
In spite of what people might desperately want to believe, these engine start losing ring seal and along with it horsepower around the 5-7 hour mark. It's a single compression ring piston design with very little skirt to support the ring package. As a direct result the rings wear very quickly and start leaking badly.
All that fantastic high rpm power your engine made new comes at a cost in the long run. It's not an XR so unfortunately you can't treat it like one at maintenance time.