'01 CR250 has lost all low-end power

[mxPro738]

A friend of mine runs an '01 CR250 with a very fast motor. Recently it lost all its bottom-end power. ??? He's check his reeds (OK), his power valve (OK), and had someone pull the engine apart to look at the cyclinder (OK) and crank (also OK). Everything checks out fine. He's at a loss and I don't have any ideas for him.

Anyone with good advice here?

 

[Hucker]

Compression test? Thats probably the first thing he should have done....

 

[dirt bike dave]

I understand the '01 CR has a very short piston life compared to many other bikes. Loss of compression due to a worn piston will kill any bike's low end power.

 

[smarttoys]

A fresh top end and a properly serviced and adjusted powervalve should take care of it. A powervalve stuck in the open position will give you no low end power.