Originally posted by Boit: Hick: Got any theories about why GRC's bike loses so much oil? Either the motor is consuming it or it is leaking out somewhere. If the return line is leaking oil may run down the breather tube, giving you the impression the oil is coming from there (ditto for a hole in left side of reservoir). But there would be so much dirt stuck everywhere any leak should be obvious. I cannot envision any scenario where a substantial amount of oil escapes out the breather, there is too much free space under its outlet. If a cam cap broke oil might spray around the outlet enough to create a problem but by that time losing oil is no longer your main problem. I’ve never measured how much oil my bike is using, I change it too often to bother checking it plus I figure there is a pretty large margin of safety. I’m sure you could run this bike successfully with much less oil than is called for in the manual, I bet the wet sump race bikes have half as much (but more means cooler which is always better). Since I don’t know how much oil we are talking about I won’t say whether or not I think it is a problem. As for the engine noise I’m always going to guess CB drive gear on any 2000 YZ/WR.