Does anybody know the part number for this o-ring:
i don't believe there is a part number for that O ring. technically, I don't
think it is referred to as an O ring,
since it has square sides. I was told they rarely leak, and I reused mine. I suspect you could check with a
local bearing shop, but it looks more like something you might find in a caliper rebuild kit.
the small seal on the front of the motor, does have a propensity to leak, and that seal is available from
Honda motorcycle part number 91209-MC5-000.