Here's something else that might be worth trying if you have a leaky seal.... Yamaha used both a gasket and an o-ring on the housings. Considering all the fastener holes are blind holes, it's a somewhat unusual arrangement. Normally on a setup such as this, you'd use a gasket or an o-ring... but not both. If you were to remove the gasket and just use the o-ring, this would move the seal lip in by the thickness of the gasket. That ain't much... but it might just be enough to get it off the worn part of the cam and onto a cleaner sealing surface. Considering it won't cost anything... might be worth a shot. EDIT: You would first need to measure the flange on the housings and make sure there's enough room from the face to the cam bearing so you're not side loading the bearing (not pushing against the outer race).