I have gone thru about half a quart of oil in 100 miles and don't know why. It dosnt smoke it dosnt leak at all. It may smoke but I cant see it if it does. Ive had to replace the cam and rocker cover because it was extremely worn out at only 4800 miles so there may be something real wrong here I just don't know. I think the top end may still be suffering from something as it makes noise but as ive never owned a rfvc engine before I dont know what they should sound like. Also are the xr and xl rocker assemblies built different as the xr rocker cover I used had much freer movement on the rockers. Someone told me that the xl rocker setup was probably built to be quieter and the xr wasn't anyone know? Anyway I guess the main question is can my bike burn about a quarter to half a quart of oil without seeing any smoke? Guess I should do a compression check anyone done it to one of these engines before it seems like it may be difficult as the plug is so hard to get to.