Very fast oil leak - A7

[BSALarry]

Hello. Well just finished rebuild on magneto and automatic timing gear...setup the timingsand it started 2nd kick. Seems to run fine...however I now have a very fast oil leak on the left side of bike. It stops when engine is stopped. I ran bike on centre stand and looked under bike and could see oil leaking from the gearbox shaft to the outer gear. The shaft is always turning when the bike is at idle and turns the read wheel very slowly..which I can stop with my hand. So, seems I have solved my magneto and rebuild auto timing gear...and how have this oil leak. Any thoughts? Would this most likely be the oil seal? My bike is 1955 BSA A7 Swing arm. I can see small hole in gearbox that must be breather..and oil is not coming from there. Not sure what is involved right now if oil seal needs replacement. Any help is appreciated.

[trevinoz]

Larry.
            If your engine had been standing for some time, the leak will most likely be the sumpfull being pumped out of the breather.
Did you check your oil tank level before you started the bike?
Trev.

[BSALarry]

Trev
Yes I did check the oil and the tank was very low..I just thought that it had gaviity feed into the sump and would be pumped back into the tank as it was running? Maybe that is why I have the check valve on the pipe leading to sump. I dont tend to use as I dont want to forget I have turned it off. So..I take it that the oil in sump is at pretty high level, and while it is being pumped back into tank...the overflow is being forced out of the breather? I did look at that area and could not tell if it was coming out of there...looked more like the oil was coming out of shaft...but it has never leaked like this before...would expect it to be slow leak and get worse over time. Do I let it continue to get pumped out while running until the engine is equalized? Thanks Larry

[trevinoz]

Larry,
          You should have drained the sump before you started the engine. The oil was at a high level and crankcase pressure forced it out through the breather.
Your options are to drain it or let it pump out all over the floor while trying to catch it.
The oil in the sump will eventually pump back into the tank, that which is not on the floor, but it will take some time as fresh oil is being drained into the sump while ever the engine is running.
At least you didn't top up the oil tank before you started the bike. That would have made a real mess!
Trev.