soap the engine down good with laundry soap and a brush, hose it all off and let it dry - make sure the oil is really coming from where you think it is.
I thought the drive shaft output seal was leaking on the back of my 650 engine a few years ago. I was getting a few drips on the garage floor right where the drive shaft comes out of the case, and there was oil everywhere on the engine case and cylinder fins, like the spinning drive shaft was throwing it.
It was actually the rear tappet cover all the way on the top of the rear cylinder head. Oil and grease have an un-believable ability to creep across metal surfaces and propagate across the engine case on it way to dripping on the garage floor.
The tappet covers have an o ring "gasket", if you dont change that oring when you adjust the valve clearance there is a chance it will ooze oil.
Im not saying your mid-drive seal is not leaking... just make sure before you tear into the motor.
These engines are very reliable, and a shaft seal leaking for no reason is rare. Having a o ring ooze after pulling a tappet or other engine cover off for maintenance is very common if the oring was not replaced.
Last edited by KCW; 02-01-2019 at 06:35 AM.