C15S 1959 Oil Pump total oil loss from oil tank

[TDub62]

Hello, I'm putting together a previously abandoned C15S project (1959). The engine was rebuilt by a previous owner (not the person I bought it from) so history of what has been done is a little vague. Last weekend I primed the oil pump by putting oil down the push rod tubes and have had a dribble of oil pumping back on the return pipe (on kickover). Today i retuned to the bike to find the litre of oil that I put into the tank is now in the sump. I removed the sump plate to look at the scavenge valve. All it seems to have is an open tube with no sign of a ball or spring. I can insert a rod 30mm into the tube before it reaches a restriction. Should there be a ball and spring in the tube?
Thanks

[AWJDThumper]

The are two non-return valves (NRV) in the engine, one for the feed side from the tank and the other for the return side to the tank. The one near the sump should have just a ball bearing in it but no spring (works under gravity). However, this return or scavenge side NRV doesn't do a lot. The one that normally stops oil draining from the oil tank into the sump is on the feed side and is either in the outer timing cover (for end fed C15's) or in the RH crankcase for the earlier models.

[TDub62]

Thanks for that I'll get back on it when I've warmed up a bit!

[TDub62]

Does that mean splitting the cases to check it out?

[AWJDThumper]

Just noticed you have an earlier C15 which, unfortunately, means you would need to split the crankcases to get at the feed NRV - not one of BSA's best design features

[TDub62]

Ouch not good news, is there any sort of test before i set off stripping it down. I haven't split one of these before is there a good manual anywhere?

[AWJDThumper]

I wouldn't rush to take the engine apart - it's a lot of effort for a very small NRV. I would run the bike a bit and see how it performs over a longer period of time. In the meantime, you can always clamp the rubber feed pipe from the oil tank to stop it wet sumping over night.

[ducati2242]

you could think about one of these . www.ebay.co.uk/itm/6-8-10-12-14mm-BSA-Norton-Matchless-AJS-Vintage-Classic-Anti-Wet-Sump-oil-valve/181878137689?hash=item2a58c82359:m:m06-amOfqArhOMLO1gdGKAw . Not sure how good they are as I have never used one .

[ANDY HIGHAM]

Anything fitted between the tank and pump can cause engine damage, gear pumps are good at pumping but not so good at sucking

[TDub62]

Ive just put 500ml oil back in the tank and will see how much has drained from the sump in the morning. Not buzzing about splitting the engine but not convinced by the valves on the infeed pipe as there seem to be conflicting stories on their success rates.
Thanks for the info.

[AWJDThumper]

If the engine is wet sumping, it could be due to a problem with the feed NRV and/or it could be a problem with oil leaking from the oil pump before it gets to the NRV. The latter can occur around the mounting face due to distortion or a problem with the gasket. Once you've taken off the inner timing cover you can then get at the oil pump and check if it's leaking oil. In principle, with the pump removed, you can then more directly test whether the NRV is working ok and blowing through with an air line might clear any obstruction if you're lucky.

[GUY HUTCHINSON]

Thanks for that, at least there is hope of a solution without splitting the cases. I'll take the inner timingcase off at the weekend and have a look.

[AWJDThumper]

If the engine hasn't been run very much, I would definitely put some miles on it first before coming to a final decision on whether the feed NRV is a problem. If you're lucky, it might even cure itself after enough oil has been pumped through the it.

[TDub62]

Hello thanks for the help again. i stripped the oil pump which looks ok. i think the NRV bearing may have been stuck. Its free now. Can you tell me which hole leads to the inner NRV?

Sorry but another question. Before stripping the bike I checked to see if oil was going back into the tank. The pipe that i thought would let oil back into the tank appears to be a sealed tube that sweeps upwards and ends up inside the filler cap opening. I checked inside with a mirror but couldn't fathom out how the oil would return. No doubt I'm missing something obvious!

[TDub62]

the other pic