I've been asked to have a look at a friends WR400 that has suddenly become low on power and is overheating. He's changed the plug and said that it was white. Having looked at this site a few times previous I was guessing that the woodruff key on the crank had stripped due to a loose nut. This was tight. It's not losing coolant or pressurising the system. Compression is good and it seems to start ok. Any ideas before I strip the carb? It does tend to run better with the choke out. Are there any concerns with the cam timing going out of sync? Any help would be gratefully received, cheers.