it most likely came from the crankcase breather, my modded DVX does it quite often. My buddies honda 450r does it too. we both race and constant high rpms are what do it. I've tried to fix it many ways but i finnaly added a K&N breather on an extended hose and placed it in the spot where the tool pouch used to be with a paper towel under it.
2004 DVX 400
-FST 500 big bore/stroker, cams, valvesprings, revbox, ported head, Yoshimura full exhaust, Edlebrock carb, custom airbox/batterybox and headlight eliminator, elka shocks, janssen swing arm, gibson a-arms and steering stem, LSR gusset kit, AC nerfbars and bumper.
2008 KTM 525
-Rath nerfs and bumper, KTM a-arms, Twin-Air filters, Hiper wheels with razrs, precision dampener, Flexx bars, bored carb, 13:1 CP piston, 806 cam, Weapon exhaust, Renthal chain and sprockets, quad-tech hood, FourWerx parts
-2009 sponsors-661, Oneal, Works Connection, CP Pistons, SMX Optics, Amsoil, Weapon MX, Twin Air, Renthal, ASV Inventions, Steve's Sports Center, Chuck's Welding and Repair