Author Topic: Another gearbox oil leak topic  (Read 252 times)

Offline ivan_j

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Another gearbox oil leak topic
« on: 10.07. 2020 20:41 »
New member here.
I'm rebuilding a 1963 Super Rocket.
In gearbox all bushes, seals and gaskets are new. Bearings, gears and shafts are good. Just input shaft used to have wear marks under the bush - grinded to closest seal size and new bush made to size.
The problem - heavy oil leak behind the sprocket. Oil seal's bed in case have slight damage but as I can see it seals against bearing too so it shouldn't be the culprit. Another suspect are the bearing marking. They are concave and oil dripping from there is possible too.
There's another leak from speedo cable, that I have to sort out too.
Thanks for replies.
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Online berger

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Re: Another gearbox oil leak topic
« Reply #1 on: 10.07. 2020 20:46 »
I stopped the leak like this, speedo drives can be stopped leaking on the fitment but not on a poorly crimped cable
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Online muskrat

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Re: Another gearbox oil leak topic
« Reply #2 on: 10.07. 2020 21:10 »
G'day Ivan  *welcome*
Could also be leaking between the main shaft and the output shaft. SRM make a nut with a seal to stop this. I have one (made by a friend down here) that did the job.
Cheers.
ps: now go over to Introductions and tell us your story. Think your our 1st member from Bulgaria.
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Online morris

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Re: Another gearbox oil leak topic
« Reply #3 on: 10.07. 2020 21:22 »
SRM sprocket nut will at least stop the main shaft leaking. Speedo drive is another question. A search for “speedo drive leak “ will bring up some modifications done by forum members which may work... or not *dunno*
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Offline ivan_j

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Re: Another gearbox oil leak topic
« Reply #4 on: 10.07. 2020 21:30 »
As I said all bushes are new, so no play between input and output shafts. There is SRM nut there too.
The oil leak is from behind the sprocket so input shaft is not suspected.
I also found the sprocket is touching the oil seal and bend it slightly. But the seal lip is ok.
Yes there are not many classic brit bikes in Bulgaria.
I'll post some pictures and info when the bike is ready.
Thanks for replies.
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Offline ivan_j

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Re: Another gearbox oil leak topic
« Reply #5 on: 10.07. 2020 21:40 »
I stopped the leak like this, speedo drives can be stopped leaking on the fitment but not on a poorly crimped cable
What's this - silicone sealant or epoxy glue?
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Offline a10gf

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Re: Another gearbox oil leak topic
« Reply #6 on: 10.07. 2020 21:53 »
Think your our 1st member from Bulgaria.

One more :O) > https://www.a7a10.net/forum/index.php?topic=10017.msg73503#msg73503

& as mentionned, a few words *(& pics) in Intro & Stories is always appreciated.
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Online morris

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Re: Another gearbox oil leak topic
« Reply #7 on: 10.07. 2020 22:05 »
As I said all bushes are new, so no play between input and output shafts. There is SRM nut there too.
The oil leak is from behind the sprocket
A sealed main bearing instead of an open one is also quite good to keep the oil in.
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Online berger

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Re: Another gearbox oil leak topic
« Reply #8 on: 10.07. 2020 22:15 »
ivan silicon sealant , it stops the oil creeping out from the ball race and around the seal and circlip when it is stood on the side stand, took ages to find out it was a problem always thinking it was coming from the bush and shaft or sprocket and seal
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Online berger

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Re: Another gearbox oil leak topic
« Reply #9 on: 10.07. 2020 22:20 »
morris my idea was a sealed bearing but I found it creeping out between the seal and the outer race, hence the silica sealant that has now put a stop to the drips
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Offline ivan_j

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Re: Another gearbox oil leak topic
« Reply #10 on: 10.07. 2020 22:35 »
Think your our 1st member from Bulgaria.

One more :O) > https://www.a7a10.net/forum/index.php?topic=10017.msg73503#msg73503

& as mentionned, a few words *(& pics) in Intro & Stories is always appreciated.
It's Duncan's bike, I'm just working on it.
I'm restoring bikes and will introduce myself but please be patient, I want to finish this bike and will show you some of my restorations.
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Online chaterlea25

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Re: Another gearbox oil leak topic
« Reply #11 on: 10.07. 2020 22:44 »
Hi,
If the seal circlip is not seated properly into the groove leaks will happen
It can be a right pain to get them into place, work around the circumference with a pin punch can help
Fit the circlip in place beforehand and measure the gap between the ends.
when the seal is fitted you have to keep working on the circlip to get the end gap the same
If the casing is scored where the layshaft bush is fitted oil will leak there too
Add a little silicone sealer where the selector rod comes out through the case as well

John
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Online JulianS

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Re: Another gearbox oil leak topic
« Reply #12 on: 11.07. 2020 10:05 »
It is worth renewing the seal retaining circlip. The originals do tend to be a bit distorted and difficlult to fit.

When renewing the seal about 12 months ago it came with a new circlip which had drilled holes to take a conventional circlip plier. Fitted straight in with no problems.

The other fitting issue is that some seals are very slightly larger outside diameter than the originals making fitting between difficult and impossible.
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