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Topic-icon '82 R100: Strange Leak Behind Front Cover

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1 month 1 week ago - 1 month 6 days ago #6659 by 2752
This is the strangest oil leak I've ever seen. 1982 R100, 42K miles. Last winter I did a fairly extensive replacement of seals and gaskets to fix numerous oil leaks, most of which were simply due to PO neglect and the obvious 38 years of life. I pulled both cylinders and replaced all gaskets and seals and cleaned everything up. I pulled the front cover, alternator, and bean can and replaced all seals and gaskets, as well as upgrading the alternator to the Omega 600 watt unit. I've run it about 600 miles since this work (lots of other stuff, too, like carb rebuilds and fixing leaks on the final drive and transmission) and it runs superbly, with no leaks . . .

Other than this one: I'm seeing a leak that shows up at the bottom of the front cover. Pulled the front cover and I see that the leak emanates from one of the little round nuts (Allen key used to tighten) that holds the inner cover to the engine. FWIW, it's the one on the right side of the bike. So, to be clear, the inner cover is held to the engine by a number of socket head cap screws, but in two places there are little 6 mm studs sticking out from the engine and two of these round nuts (Allen key used to tighten) are used on these.

WTH? I cannot tell from the parts microfiche (MAX BMW) whether a wave washer is supposed to be used under this nut; none was present when I disassembled it, but I know someone was there before me. I added a wave washer, but that made no difference. I am about to install an o-ring that fits tightly over the stud, then install a wave washer and the nut. But obviously that's not OEM, and it didn't leak when it was built.

I didn't leave anything out when I put it together, like the two little spacer gaskets that go above the main gasket between the inner cover and the engine.

Any suggestions?
Last edit: 1 month 6 days ago by Wobbly. Reason: Mods altered title

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1 month 6 days ago - 1 month 6 days ago #6662 by Wobbly
Replied by Wobbly on topic '82 R100: Strange Leak Behind Front Cover
Only thing I know is the oil seal behind the alternator and then the o-ring where the crank shows through.
It's very easy to pinch that o-ring !

Don't hide 'em, Ride 'em !!
#15150
Last edit: 1 month 6 days ago by Wobbly.

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1 month 6 days ago #6666 by 2752
I'm having trouble finding which o-ring you mean. Only o-ring I can find on the fiche is the one at the rear of the crankshaft. Just a bearing at the front.

You don't mean the o-ring on the bean can?

Everything is dry behind the front cover except the area below the stud/nut I mentioned above.

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1 month 6 days ago #6667 by Wobbly
Replied by Wobbly on topic '82 R100: Strange Leak Behind Front Cover

2752 wrote: You don't mean the o-ring on the bean can?

Yes, guess so. Sorry, working from memory and not from the fiche.

2752 wrote: Everything is dry behind the front cover except the area below the stud/nut I mentioned above.

A photo would help.

Don't hide 'em, Ride 'em !!
#15150

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1 month 6 days ago #6668 by 2752
Going out to the garage with a camera now. Should have a photo within an hour or so. Thanks!

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1 month 6 days ago - 1 month 6 days ago #6670 by 2752
I guess I don't know how to insert photos in this forum. I'll try again.


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