worn out?

[tristan18au]

hi i have an 1998 XR250 with a problem. it keeps rattling in the engine.it has compresion and runs ok when you get ridding. But alos when i forst start it when its warm it splutters then comes clean. could it be valves? The valve clearance is spot on so what is it??? please help!!:eek:

 

[snaggleXR4]

Rattling in the engine surely sounds like valves to me. Triple check your valves. I believe the cam chains on newer 250's and 400's have an auto tensioning mechanism, so unless it's broke, it shouldn't be the cam chain. If it is really bad, get it checked out. Maybe engine knock? Run higher octane fuel, especially if you have a high compression piston kit installed. Good luck.