oil blowback?

I have absolutely no idea what your question is, what bike you're driving & hence no contributor's replies to your thread.

I'll take a punt on guessing that the engine upgrade you did is putting a lot of back pressure on your standard crankcases because you probably over compensated by topping up the size of the new lump with too much oil?

The engine overflow is like a crankcase safety blow off valve which lets excessive oil escape from the engine through the breather hose but unfortunately is in the path of your rear wheel.....

steo
July 2009