I just would like to share what happened to my 15 year old brothers bike. I am not blaming Yamaha or anything, but my brother. He bought a 2007 yz 250f for $700. It had a bad crank bearing. He and my dad spent $900 in parts to rebuild the engine from top to bottom - new cylinder, new crankshaft and bearings, piston, oil pump. Basically everything except for the head, valve cover, and cases. When rebuilt, the bike ran great. I mean, the bike didn't have a problem at all, except maybe it could use some re-jetting as there was a bog somewhere between closed and a quarter throttle. Well, my little brother likes to ride up and down the highways, revving his bike out completely. He thinks that the rev limiter "sounds cool". The other day he called me to tell me "his bike just locked up". got the bike tore down yesterday, and he floated 2 of the valves, destroying the head, and dropping the valves (which shattered) into the piston. I'll post pics when I get to my phone. He had been redlining it in spite of our warnings that it would destroy his engine. basically, the moral of the story: If you think the rev-limit sounds cool, things get crazy expensive.