After a very dusty day at the TT Day at the Ridge a few weeks ago I was checking my valves and found that the clearance had gone to zero. I pulled the motor and while cleaning found that the breater line from the airbox to the head had a 1 1/2" burned through crease where the hose had touched the header pipe. The intake had been sucking unfiltered air for at least part of that day. I dont know if the dust played a part in the valves going out of limits or what, but... When it goes back together in the next few days I will make sure that hose is routed clear and zip tied to prevent this again. Check your hose.