Transmission oil leaking into motor oil!! Need Help!

[zawetzel13]

Ok, so I went riding this past weekend for the first time on a used 07 450ER that i just bought. I looked over everything to the tenth degree before going out. oil in both the tranny and the motor side were right where they should be.
After about 5hrs of riding i check the oil in the sight glass and see nothing but oil all the way to the top. so i check the tranny oil by taking the oil fill bolt out and tipping the quad up on one side... nothing comes out.
I'm thinking??? ok, this can't be good. i put some oil in the transmission (a little over 400ml) to fill it up and drained the motor side and filled with new.
I'm sure somehow oil has leaked from the tranny to the motor side of the engine, all with no leaks on the outside of the motor. the vent hoses are not plugged and seem to be breathing just fine.
Any help would be greatly appreciated

[Scro]

It's more than likely the crank seal on the clutch side. It's not hard to replace. Just remove the clutch basket, and you should be able to pick the old out, and put the new in. Be sure you pay attention to which way the old one came out. If you put the new in backwards, it will ruin the new seal.

[zawetzel13]

I was hoping it was something easy, i knew it must be something internal, so i was really worried. I'll tear it apart tomorrow and reply on what i find out.

Thanks a bunch

[Scro]

The bad part is you really can't tell if it's that seal unless you replace. It will visually look alright. 90% that is what causes the oil to swap though.

[turbo j]

I have this same problem and I am doing this exact thing tonight. I ordered the oem seal and went to put it together Monday night and it was to small. Oh ya, I have the new and improved crank bearing collar and seal. So I have the correct seal now and hopefully this fixes the problem for me.

Scro, Thanks for adding that the seals normally look fine but can still leak. That helps my confidence that this should take care of it cause the old seal did "look" fine.

This different size seal probably only applies to 04/05 owners who have had the update done.