Letter Of The Week

Get Your Head Checked
I own a 2007 CRF250. I stay on top of valve clearance checks every 6 to 8 hours. The bike has 25 hours total. The initial clearance from the start on one of the intake valves from factory was .0045" (shim 1.95). It has never moved. My last check was 7 hours ago. I rode very little over winter (Ohio). Bike would not start and found 0.000 clearance on the intake. I had to go to a 1.70 shim to provide .007" clearnace. Question: should I pull the head? How often should one keep shimming versus doing headwork? I do not ride the bike like crazy and hit the rev limiter like most people at the track. I just don't want a melt down; this has me very concerned. Can you please provide some guidance?Josh Seigley
Risingsun, OH
You can shim the valves once, but if they move again, then you need to change them. It seems odd that you have seen such a radical change in just 25 hours. Dirt getting past the air cleaner or water getting through the air cleaner is the usual reasons for the valves to go soft. For now, keep a close eye on the clearance, but as we said, if they valves get tight again have the head checked out by a professional you trust. -Karel Kramer