C15 - another oil feed problem

[cee-b]

I have a recurring (and very baffling) oil feed problem and would appreciate any help please.

The story so far:

I have checked that the oil flows freely (though surprisingly slowly) from the oil tank. The filter is clear and there are no blockages. The tank vent is fully functioning. I have changed to 15W30 fully synth oil as it is the thinnest (therefore fastest flowing) oil that I have.

I have primed the pump by removing the spark plug and turning the engine over on the kick start while pushing oil under pressure down the pipe from a syringe. Oil flows into the pump on cranking and oil returns through the scavenge line to the tank (all pipes are clear plastic so I can see the flow).

On starting the engine, oil can be seen feeding up the scavenge line to the tank return and to the rockers etc. Because this oil is slightly aerated, it is easy to see that it is flowing. I cannot see whether the oil in the supply line is actually moving as it is quite clear and un-aerated.

This continues for a short period - possibly up to a couple of minutes. After this period, the scavenge line begins to show large air bubbles in the oil flow and the supply line has large air bubbles appear from the pump end and float up toward the oil tank. Oil clearly stops flowing to the pump at this point and the pump becomes airlocked.

Following this, the pump will not work until the priming process is repeated.

I don't really want to have to split the engine and start investigating the pump unless I really have to (and the pump appears to be working when I turn it by hand.

Any thoughts please guys?

[JulianS]

If it was my bike I would do the following;

1. Make sure the oil pipes are connected the correct way around.

2. make sure the flexible pipes are not trapped or squashed and that they are in good condition.

3. Make sure the oilways in the connector block on the crankcase are not obstructed .

4. With oil in the tank, remove or losen the connector block and allow oil to flow from the tank via feed line to remove any air lock. Retighten when done.

5, Prime the sump by introducing some oil into it via tappet cover opening.

Then try it again. Oil in the return side will be aeriated due to the larger capacity of the scavenge gears in the pump.

If you get another airlock in the feed side and all the unions are secure and pipes good then you need to investigate the pump and its joint surface with the engine. If you bike is not a later C15G engined one, then the early pumps do distort and sometimes can hardly be rotated by hand. 

[cee-b]

Thanks Julian,
taking your points 1 at a time:

1. The supply is on the outer (RH) pipe of the connector block. This is the way it is shown in my BSA service sheets and, as the scavenge oil goes in the right direction, I can only presume it is correct.

2. All pipes are new and not trapped.

3, 4 & 5. I followed your advice and did this.

I ran the bike again - no change.

I have jury-rigged a clear plastic bottle with a direct feed to act as an oil tank to rule out any feed problems from the bike's tank. Using this method I can confirm that the oil level does not drop with the engine running - the oil pump is not drawing oil.

Either my priming method does not actually work or the pump is sucking air in.

Looking at the Service Sheets, stripping the engine to get to the oil pump seems a bit daunting (I am new to all this). Is it within the scope of a novice bike mechanic or do I need to be looking for a proper spanner monkey who knows classic bikes?

[JulianS]

Most of us learned our BSA mechanics by practical experience and for many that is part of the fun of owning an old bike. Finding a motorcycle mechanic who really knowss old bikes is not easy and can work out expensive, the hourly rate will be about the same as for a car mechanic.

Getting you pump out is not that difficult - 4 nuts and 3 screws. easiest with the bike/engine on its side. take the sump off, undo the pump securing screws and jiggle the pump out. There should be a gasket between pump and crankcase.

Photos from Pitmans Book of BSA 250 and 1961-62 C15 parts book.

[cee-b]

Julian, you are a star.

Looking at the service sheets, it seemed that it was necessary to remove and split the engine to get the pump out. It looks like I need a more comprehensive workshop manual in order to avoid unnecessary jobs - maybe the Rupert Ratio book?

[JulianS]

Rupert is a good book and very helpful.

Parts book also useful.

Good luck.

[cee-b]

I've just tried tracking down the Rupert manual - rocking horse sh1t springs to mind. It looks like being a Haynes; I'll also look for a parts book.

Thanks again for your help Julian - I'll update when I have some results.

[cee-b]

Here is the update. GLOOM!

I have gone in through the sump and it doesn't matter how much wiggling I do, that pump is not coming out through that gap; the pump body is considerably bigger than the aperture.

Is there a bigger pump that may have been fitted in the past?

Either way, it looks horribly like the only way to get it out is to split the engine - unless anyone else knows differently??

[JulianS]

No bigger pumps.

I think it was me misremembering getting the pump from my B40 as being done that way and easily. Sorry to give you false hope of an easy job.

The only way is removal of the outer then inner timing covers, the later not being so easy because of the gears. Rupert ratio suggests it can be done without removing the primary transmission but warns that it is not the prefered method.

[cee-b]

Thanks Julian,
I'll wait until the Haynes manual arrives then give it a go.

At least I had 1 night of thinking it might be easy!

[cee-b]

New pump and gasket fitted and the problem is solved  I did it by the 'not preferred' method; it was tricky to reassemble but not too bad.

The bike now seems to fully functioning but with a bit of wet-sumping.

Thanks for the advice and assistance

Col

[MICKREEVES]

You  should be able to find the Rupert Ratio book on Ebay.
Mick

[cee-b]

You  should be able to find the Rupert Ratio book on Ebay.
Mick

Thanks Mick, I'm keeping an eye out.
Col