Topic: 1975 Honda CB750F1 Crankshaft Shaft Seal

[RodSOHC750]

The new shaft seal has rubber lips on one face and a metal face the opposite side.   I've searched on which side faces out but unsuccessful so far.  Which side faces out for the crankshaft oil seal?

[HondaMan]

The new shaft seal has rubber lips on one face and a metal face the opposite side.   I've searched on which side faces out but unsuccessful so far.  Which side faces out for the crankshaft oil seal?

The metal side goes toward the crankshaft. It deforms to make a strong oil seal backing plate when you torque the cases down.

[RodSOHC750]

I noticed the seal I removed has a small lip that fits in the machined groove in the case bore.  The seal in my kit does not have this small groove.  If I use HondaBond on the outside diameter of the seal, should this seal work ok?   Without the lip, future extraction might be easier?   

[HondaMan]

That lip is formed when the cases torque down, and it forms the seal. This seal cannot be extracted and inserted without opening the cases, or else it will leak afterward(!). When the metal-backed seal is new, it has not lip along the face until the cases are clamped down on it. Directly behind this seal is a 60 PSI oil port (the #4 crankshaft main bearing), so the unusual seal is a special design to hold back all that pressure.