Oil leak

[bikerbob]

Hi there   Just been out for a run on my A10  Flash no problem with the run but when I came back I did something which I have never done before which was when I drove up onto the drive I put the bike on the side stand with the engine running while I opened the garage door and when I looked round the bike was pumping oil onto the drive. I quickly picked the bike up and drove into the garage stopped the engine put it onto the centre stand then started the engine again no oil coming out is this because it was on the side stand or is it something else. I normally stop the engine on the drive then put on the centre stand before opening the garage and then push the bike in. The only other time I have had something similar was about 10 years ago when I left it in the garage for about 2 months without running it this was obviously due to wet sumping and now I never leave it for more than 3 weeks without running the engine or if I do I drain the sump prior to starting.

[Topdad]

Hi I can't say if the bike being laid over could cause the oil to pour out as you describe but how's the oil level in the tank ,have you had to top it up recently if so and the sump had more in than normal it could have vented into the chaincase and with the bike laid over it's leaked out of the filler cap .However,that would mean that you've acheived the near impossible ,getting the chaincase completely oiltight in the first place .I can't wait  to see what cleverer people than I  think ,should be interesting ,best of luck BobH.

[bikerbob]

Hi There Thanks for your reply but the engine oil is at the correct level as it has been since last year there is no oil going into the chaincase and it is oil tight, bike has stood over the winter for about 4 months being started up every 2-3 weeks no oil drips on the garage floor and the filler cap is on the opposite side to the side stand also the oil is coming from the same side as the side stand, also I have been on a few runs since coming out of storage with no problems like I said earlier this is the first time in about 15 years that I have ever had the engine running whilst it was on the side stand always on the centre stand with no problems.

[bsa-bill]

First thought (not always a good one)
with the bike on the side stand and possibly leaning more than usual ( soft ground, camber on drive) the oil tank breather would be lower than normal, if also the tank was maybe over filled slightly then oil would leak out of the breather?
No more than a possibility methinks

[bikerbob]

Hi there thanks for reply just been out to check and with the bike on the side stand the return pipe discharge hole in the tank is just below the level of the oil in the tank maybe this is what caused the problem.

[chaterlea25]

Hi Bob,
When the bike is on the propstand and the engine is running, the oil return suction pipe is on the high side of the engine, this allows a build up of oil in the crankcase until the level rises to the pickup pipe!
The excess oil is then blown out through the breather 
HTH
John O R

[muskrat]

 Are you sure it's not gearbox oil?
Cheers

[bikerbob]

HI there.  Thanks for the prompt replies and I think chaterlea has given the most likely cause of this problem it was running for a few seconds before the oil came out and I will certainly never leave the bike running on the side stand again don't really know why I did it as I say I normally just put it on the centre stand. Muskrat the oil is engine oil not gearbox oil.

[bikerbob]

HI there. Just an update on the problem, I have had a reply from someone in the BSA owners club who says he regularly uses the side stand while the engine is running sometimes for as long as 5 minutes maybe longer while he puts his gear on and has never had this problem. He also says that the scavenge side of the pump runs twice as fast as the live side so any build up of oil would be returned to the tank and any excess would be returned back to the tank as soon as it was stood up but maybe my bike leans further over. I am about to do my annual oil change but am waiting for a new cartridge filter which I have fitted in the tool box, been in for about 12 years now changed annually. Giving this some more thought now it could be maybe I have to much oil in the tank, I tend to fill it till it is just below the return hole and when the bike is on the side stand it covers that hole, I did take the seat off and checked and oil did not come out of the oil tank breather.

[duTch]

Not sure which model flash?? Did you not get to narrow down leak zone- left/right front /centre?
  Someone correct me if I'm wrong,but return pump is at same speed, gears are same diameter but return gears are wider so it pumps more.
 Also re Chaterlea John, surely the suction pipe is low enough to not allow that much excess unless the ball in the bottom momentarily stuck shut ????
  Best thing I can suggest is ride it and see if problem persists,(take a drip tray>bucket)
     cheers,duTch

[bsa-bill]

Hi Dutch I could be wrong but I think what John meant was that with the bike leaning oil in the sump would move away from the suction pipe for a short while as it found a new angled level (deeper at the drive side and shallower at the timing side) once it rose high enough to reach the suction pipe (it might take some more time for the suction side to prime) then it could wet sump until it cleared.
I'm sure John will correct me if I have this wrong but it sounds like a plan to me

[bikerbob]

Hi Dutch.  The bike is 1957 and I am sure the oil came from the crankcase breather I have been on a few runs since coming out of winter storage and no problems bike running fine. But on that day I put the bike on the side stand with the engine running and oil was leaking from underneath as soon as I stood the bike up it stopped . I stopped the engine pushed the bike into the garage put it on the center stand started it up no oil leak. I rarely use the side stand because a few years ago it snapped and just caught the bike in time I fitted a new one but have always been wary of it but the other day when I came back off a run for some unknown reason I put it on the side stand with engine running while I opened the garage door. I also have an A65 and when both bikes are on the side stands the flash does lean further over than the A65 I know they are different bikes but the A65 has the original side stand and the flash has a pattern one maybe it just leans to far over and the oil builds up in the crankcase  and then blows out of crankcase breather  before the scavenge pipe can pick it up.  I will not again let the engine run whilst it is on the side stand, to much of a mess to clear up.

[chaterlea25]

On the ball!! Bill