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Gossamer
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Joined: Fri Jan 05, 2018 9:49 am

help

Post by Gossamer »

Can anyone tell me why oil is pooling back here or where it may be coming from?

Lost about half quart in 25.miles
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jwonder
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Re: help

Post by jwonder »

The pictures are hard to decipher and I will explain why. There are two places for this to leak (other than the oil pan gasket itself) and both are not very good.

1) It looks like it is coming from the back "shelf" part of the motor that goes under the gearbox in the rear of the engine. That the first picture as to location. The second picture shows oil on the shelf, but it does not look like that much. Could be it was on the side stand and it ran out. Either way, if it is leaking on the shelf and then to the ground it is coming from one of two places. The rear main seal of the crank (in the block) or the front seal in the gearbox. If the clutch is not slipping it is coming from the rear main seal. If the clutch is slipping it is coming from the gearbox.

2) The last picture you show is of the front breather tube on the front of the motor which seems to have a drip on it. If it is leaking from there then you have a breather timing issue (if its a fresh rebuild) or some other bad issue that is making the front timing case fill with oil.

If you let us know if its from the front or back we can narrow it down. Also if the clutch slips when riding. That much oil is not good but the good part is if the engine is okay and the rings are good replacing the seals is not a horrible job.

How many miles on the engine?

Was it sitting for a while?

Any more info would help.

Best!!
James Wonder
Long Island, New York

Gossamer
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Joined: Fri Jan 05, 2018 9:49 am

Re: help

Post by Gossamer »

117 miles on rebuild.

Thinking it's blow-by issue since most the oil seems to be coming from breather tube.

Oil is too fresh to look that dirty already

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jwonder
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Re: help

Post by jwonder »

Sounds like blow-by or other issue. I would check everything on it even after you found it on a fresh rebuild. Never know what else was missed.
James Wonder
Long Island, New York

bellsonracing
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Joined: Wed Nov 16, 2016 11:55 pm

Re: help

Post by bellsonracing »

My vote is on the rear main oil seal. The breather would not cause the build up on the shelf.
A bad rear main seal pools a lot of oil on that shelf, and then it all pours out when you put it on the sidestand.

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miller6997
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Re: help

Post by miller6997 »

In my experience, the oil that escapes from the breather can create a film of oil on the underside of the bike and a few drips in the garage, but it happens mostly when the bike is underway. Is it likely that it would produce that BIG puddle of oil shown in one of the pictures? Even the Nortons and BSAs in my ancient past never leaked that much. On the other hand, the oil shown on the tray is a trivial amount (I sometimes wipe away about that much after a long ride) and I see no "bathtub ring" that would suggest that a substantial amount has been accumulating there.

A head-scratcher, for sure.
Last edited by miller6997 on Sat Jun 19, 2021 5:16 pm, edited 1 time in total.
Jon Miller
'67 R69S
'13 F800GT
Altadena, California

Andrew
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Re: help

Post by Andrew »

Hi ,I’ve had similar problems regarding the oil that was from the rear oil seal it gathers where you can’t see under the “tray” of the crankcase between the gearbox housing and when the side stand is used that’s when if enough has gathered will drip out … now I did take my gearbox off to sort this problem .. clutch , flywheel, off and out with the seal however what I didn’t examine was the condition of the running surface of the inner boss of the flywheel( that’s what actually runs in/on the seal ) so after replacement I went out on rides for around a total of maybe 500 miles only to find it leaking again ! You can buy a press on ring that goes on that boss to cure the issue which next time I feel the urge for a strip down I shall use , in the mean time I use a piece of sponge on a wire that I slide on the shelf and ever so often I wash and dry it then slip it under again !Simples!

Daves79x
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Re: help

Post by Daves79x »

As I mentioned in another venue, the breather plate may be compromised in some way and you can check that with the engine in place. Just remove the front cover and the timing cover. Only issue is going back together if you don't have a locating circlip for the breather plate (later ones don't, and many early ones have it omitted). At least this will eliminate one thing. I guess then I'd pull the head and cylinders and do some investigating/measuring there.

Last, I would pull the trans and check the seal/mating surface.

Dave
Dave

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