When racing my 750 engine is blowing oil out around the crankcase breather.. what setupsdo you guys use as far as catch cans etc? Right now I have the stock setup and I think the reed valves may be causing some of the problem.
Run an aftermarket breather like STM, mine never leak out there anymore. The older SS and Monsters were worse. I cut the breather vent box out and run a little breather from Pep Boys ($9.99) Come in black, blue,red, yelow, chrome, etc. Be sure to cover the hole where the hose goes in the airbox.
I used to have the same problem on my 620. I solved it by running the oil level just above the Min mark in the window. I didnt change over to an STM breather till later but lowering the oil level fixed the oil in the airbox issue for me.