Okay, here are the symptoms... Oil is coming into the airbox off the vent line out the back of the case, Its a rebuild with 1k on it 101mm 10.5:1 wiseco Hotcam stage 1 stock jetted carb k&n (not over oiled) white bros e seires pipe Not a wheelie rider My buddys 400ex did the same thing after build but stopped after a min, and we did a race build on it 11.5:1 416cc I'm stumped with this thing. I know i need to do a carb rebuild on it, vacuum diaphragm, but other than air fuel mix he's fine no airbox blockage not smoking out the pipe at all except when it loads up on fuel, then its just black. I dont know what psi it should be on compression with these upgrades, but it seems the rings are seated I've got way too much money in the bike to start over. somebody please shed some light on this for me!!!