my friend has a 04 crf 230 and he took the end cape off and some people say that burns the valves. Is that true?

Thanks for all replies.

 

Without a rejet, it will be running lean and therfore hot, and yes it can toast the valves, and worse! Don't let him ride it........

These guys had an article on uncorking the 230, but it is old and not on the board anymore. Maybe you can search old stuff and find it. It gives jetting recommendations: http://dirtbike.off-road.com/dirtbik...No=2&sort=null