what could have caused this?

[old man roger]

Originally Posted by stunna dale

omr have u ever herd of the f4i pumping oil in the cylinders cuz of too much pressure in the case due to the clean air mod?! this f4i i just picked up was doin it till i took the clean air mod off. my guess is that it was building up too much pressure in the case and pushing oil past the valve seals cuz once i removed the clean air mod it quit! my f4i b4 this one i never did the clean air mod and i had 31000 miles on that motor and it never did that... parked it on the tail numerous times and i never had a prob with oil in the airbox...??? let me kno if this sounds legit cuz thats where im at with this f4i

Sounds to me like the clean air mod was done incorrectly, when done correctly it will actually create a vacuum in the crankcase, not pressure.

The f4i wont normally have an issue when on the tail, the crankcase vent on the f4i is on the top left.

The problem would happen when the bike is lying on it's left side or if it rolls over the cage and the tank and tail are touching the ground, or obviously if it's upside down.

This is a guess but it sounds like maybe some one didn't unplug the electric valve when they did the clean air mod, the valve needs to be unplugged to stay open or the system will build pressure.