Thanks again for your keen detective work. I went back out to the shop, took some photos, and
thought about it for a while. Guessing that this 57 BigTwin has been apart before by the looks
of the slop job on the sealant, and someone decided to put an o-ring in that top groove.
As you suggest, the bottom crankcase has no oil drain passage in the crankcase groove,
and an o-ring makes perfect sense there. The front crankcase cover does have a drain hole,
but above the o-ring groove a ways.
The top crankcase groove does have an oil drain passage in front case half, and as Frank says,
it would make no sense to block it……. besides, gravity should help out some here, as well as
the neopreme rubber seal at the very top.
An o-ring can’t go in the needle bearing assembly groove, as the locating pin in the crankcase half
would be against that idea.
I’ve never seen this motor run, and have no idea how long the errant o-ring was in the top of the
crankcase, but don’t see where it caused any damage. None the less, I will omit it upon
re-assembly.
Thanks! and Happy Cinco Di Mayo!
Prepare to be boarded!
