A: Oil Pipework Oil return to tank

[mikeybumfluff]

Hi, Mike here. Thanks for having me on this forum! I'm currently working on my boss's collection of motorcycles for a bit of extra cash and experience. I'm clued up with modern motorbikes and have quite a bit of experience servicing and repairing. But I sometimes struggle to get my head around the older bikes so i'm here to rummage through older posts and pick your brains for advice and guidence.

Vincent Black Shadow - lt hasnt been run for a few months so drained all the oil, cleaned filter element and replaced with new oil- Tank, G.box, Chaincase then fresh fuel. It fired after about the 4th kick, apart from it being a bit smokey for the first few seconds it seemed to run ok. While the bike was idling, I removed the oil tank cap and the oil returning seemed to splurt back into the tank rather than be a steady stream. On the BSA B31 i was working on previous, oil seemed to flow constanty back to the tank.

Is this normal? Or should the oil be returning constantly, in a consistent flow?

Cheers
Mike

 

[Bill Thomas]

Hello Mike, Yes Vincent's return in fits and farts,
Did you drain the sump ? , Vincent's , Wet Sump sometimes over Winter,
Like some other old British bikes, And that makes them smoke,
The danger is in filling the tank, And then the extra oil in the sump gets sent back to the tank,
And over fills, Getting oil all over the engine !.

The drain plug is a bolt on the left side, Where the left front prop stand swings out,
You get to it via a cutout hole in the stand plate,
You will always get some oil out, But some times a few pints !!.
Cheers Bill.

 

[davidd]

Mike,

The oil return is rather spotty at idle. It perks up as the RPMs rise. The return that you are watching is not the same as the oil going to the big end and cams (which is handled by the front of the oil pump).

The engine can run a surprisingly long time without oil spurting out the return pipe. If the sump is drained, and the oil is low in the scavenge chamber, it will take a while for the oil to build up again in the sump and be carried to the scavenge chamber by the flywheel. No harm is being done, in general.

David

 

[mikeybumfluff]

Great stuff, yes I drained the 'sump' and quite a bit of old oil did come out.
There was virtually no oil in the tank when i came to it before i started working on it. And a lot of oil was in the drip tray underneath the bike where it had been stood. Ive read they lose oil through a breather hose over time.

I was just worried the engine wasn't getting lubricated properly. As long as there is plenty of oil in the tank and it eventually gets returned, should it be good to ride?

Thanks Bill and Thanks David, its made things a bit clearer for me

 

[Chris Launders]

The explanation for the difference in oil flow from the BSA is that it has a gear pump which provides a constant flow straight back to the tank, whereas the Vincent pump is in effect a slow moving piston pump that also lubricates the valve gear on it's way back.

 

[mikeybumfluff]

The explanation for the difference in oil flow from the BSA is that it has a gear pump which provides a constant flow straight back to the tank, whereas the Vincent pump is in effect a slow moving piston pump that also lubricates the valve gear on it's way back.

That explains it, thanks Chris!