Author Topic: BSA a10 oil leak?  (Read 2810 times)

Offline Wylyetom

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BSA a10 oil leak?
« on: 24.03. 2011 21:58 »
Hi all, I am new to this forum but I seek your knowledge! I have an a10 road rocket that I use in the warmer months. Last week I decided the time was right to wake the rocket from her winter hibernation, I went through the usual routine of draining the oil out and putting in some fresh petrol, ten minutes later she was running perfectly and all was well, or so I thought? Three day light use and I noticed an oil leak from around the back of the engine, no surprise I thought, but on further investigation I found that the oil was In fact leaking out the bottom of the magneto? I have now removed the mag and it was filled with oil, I'm not sure what could of caused this, the mag seal is fine, the only thing I can think of is whether pressure has built up in the crank case? The breather end float seems correct as I fitted a new cork shim a couple of years ago, I did notice that the oil pressure release valve was very loose, I have never heard of this problem before and so am putting the question our there, any ideas would be greatfully received, Tom

Offline a10gf

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Re: BSA a10 oil leak?
« Reply #1 on: 24.03. 2011 22:36 »
Welcome to the forum. Now, that's an 'innovative' problem, the magneto filling up with oil.
It has to come trough the seal at the drive end? Can't help really, but looking forward to read about cause and cure.

e

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Offline cus

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Re: BSA a10 oil leak?
« Reply #2 on: 24.03. 2011 23:13 »
G'day Tom,
My guess is that it has had a massive wet sumping episode over winter
& oil has leaked into the magneto somewhere after you first started it, maybe along the shaft
from the timing case? This same thing happened to one of the guys in the club when he shipped
his bike o/s for the international rally, with a full tank of oil. Good idea to empty out your oil
before you lay it up for wnter, (put a big note on your oil tank though!)
regards, Cus
56 G/Flash project

Offline dpaddock

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Re: BSA a10 oil leak?
« Reply #3 on: 25.03. 2011 06:47 »
Is the mag seal oriented correctly?

David
David
'57 Spitfire


Offline Wylyetom

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Re: BSA a10 oil leak?
« Reply #4 on: 25.03. 2011 07:24 »
Hi David, the mag was reconditioned a couple of years ago, I have checked the seal and it's fine although i will be fitting a new one, the funny thing is that it never seemed to leak oil when I first ran it and only started a couple of rides later and it could be seen dripping out the mag when the bike was running?

Offline A10Boy

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Re: BSA a10 oil leak?
« Reply #5 on: 25.03. 2011 09:29 »
Hello Tom welcome.

Your mag seal MUST be defective, the only question in my mind is whether the crankcase is being unduly pressurised causing oil to blow by the seal. So the question is, is oil being blown from anywhere else, from around the dynamo cork or the rear engine breather for example? If so this would indicate excessive crankcase pressure.
HTH

Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline Wylyetom

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Re: BSA a10 oil leak?
« Reply #6 on: 25.03. 2011 10:33 »
Hi there I hav'nt noticed oil leaking from anywhere else, apart from the odd dribble from the breather on starting, I also thought that there could be too much pressure in the case, I wasnt sure whether the loose pressure release valve could be at fault? I will change the mag seal, check the pressure release valve and then see if this cures the problem?

Offline Goldy

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Re: BSA a10 oil leak?
« Reply #7 on: 25.03. 2011 16:15 »
Is it possible that the cylinder base gasket is leaking and the oil is getting into the adjacent magneto pick up. Just a thought.
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