Wierd oil leak issue, '03 YZ450F.

My new to me YZ 450 leaks oil from the bottom of the oil filter cover, at around the allen head bolt. Obviously it's not a huge leak but it's there. I HAVE replaced all o rings there and cleaned off both surfaces. The bottom bolt {all bolts for that matter} is NOT stripped and tightens down fine.

At this point I'm at a loss on what it could be. Is it possible the cover has been taken on/off so many times it's warped and not seating properly on the case?

Any ideas are welcome.

Is it a stock oil filter cover, or a slick looking black one with a big R on it?

It looks like a stock OEM piece.


If it's leaking around the Allen bolt (the lower rear of the 3), it may be that the hole was previously stripped, and too short a Heli-Coil was used to repair it. This could leave the filter well drain hole partially opened to the shank of the bolt, putting high pressure oil against the otherwise unsealed bolt shank.

Try plugging the hole as described here:


I'm betting that will do it for you.

Hmmm, that definitively sounds like a option. So this thing is just a oil drain passage? I might try that and give it a shot. At this point a little Yamabond took care of it but I'd rather not have to do that every time I pull the filter out. Thanks.

Be certain to block the correct hole (arrow). The larger one forward is the feed passage.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now