Author Topic: Oil leak (1965 B40F)  (Read 104 times)

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Phil C

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Oil leak (1965 B40F)
« on: 16 February, 2019, 19:34:07 »
Good evening all, I'm thinking, sometime soon, of revisiting an issue I spent some time on, with a lot of help from this forum, last summer. It's an oil leak which only happens when the bike is running.   The oil appears on the inboard side of the primary chaincase, but I can't see exactly where it's coming from (oh no, not that again, I hear you groan!) Last summer I replaced the seal behind the clutch and the one at the gear box sprocket (major operation and great learning experience for me!)but that didn't solve the problem. I'm wondering if the leak is coming from the grommet where the alternator wires go through the inside wall of the primary chaincase.

First of all I'll drain the oil  from the primary chaincase (via the drain screw) and take the bike for a run down the road with the chaincase empty (I was advised this would be okay, I think by AWJDThumper last year.)  If there is still leaking oil then I'll know it isn't coming from the chaincase (assuming draining it via the drain screw gets it all out.) If there isn't any leaking oil, then it would seem it's coming from the primary chaincase. So I will then take off the cover and have another look at the grommet. I looked at it last year, when I was doing the oil seals, and at that time I put on a dab of silicone, but I wonder if perhaps I need to make a better job of that (ie clean it with carb cleaner and put on a bigger dab of silicone.)

Unfortunately I can't see the other (inboard) side of the primary chaincase wall, so don't know for sure whether the grommet is the source of the leak or not.

Two questions I hope someone can please help with:

1.  Does my plan seem sensible?

2. When the alternator wires pass through the grommet in the primary chaincase wall, at the other side of that wall are they in open air? I mean, would any oil which passed through the grommet, then be splashing around in open air? I guess that's really asking is it a possible source of the leak.

Thanks in advance.   Phil.