No Oil Return on Twin

iandusud · Post by **iandusud** » Mon Jan 03, 2011 2:28 pm

I've just finished an engine rebuild on a '56 Model 20. Started her up and watched for oi circulation. Oil went down but no return. I was patient, as I was happy that oil was getting the crank, but no return to the point where the engine started floundering as oil built up in the crankcase. I've got the oil pipes the right way round! While I had the engine apart I stripped and and rebuilt the pump with new gaskets. Before I start stripping it all down again any thoughts as to what I might be looking for?

Thanks, Ian

1608 · Post by **1608** » Mon Jan 03, 2011 2:58 pm

Ensure that the paper gasket btn pump body and timing cover has not slipped. Check for blockage in return tunnel of the crank case.

iandusud · Post by **iandusud** » Mon Jan 03, 2011 3:02 pm

Thanks for the reply. What do refer to when talking of "retrun tunnel of the crank case"?

Ian

1608 · Post by **1608** » Mon Jan 03, 2011 3:07 pm

Assuming that your '56 is the same as my '60 twin, then the oil return from the crank case to the banjo fitting on the crank case ( rtn hose )is connected by a tunnel which is cast into the crank case body.

Correction - the tunnel runs btn the bottom of the crank case and the rear of the oil pump. The tunnel casting is quite visible on the outside of the crank case.Edited by - 1608 on 03 Jan 2011 3:12:17 PM

iandusud · Post by **iandusud** » Mon Jan 03, 2011 3:11 pm

OK thanks,

Ian

Eric · Post by **Eric** » Mon Jan 03, 2011 5:40 pm

Did you have a workshop manual available when you did the engine re-build?

This details that the return oil way should be checked and a method of unblocking it, fortunately it can still be done afterwards.

Check the position of the paper gasket as 1608 suggests, but on both pumps as the return oil pump is primed by the feed pump and is otherwise incapable of lifting the oil from the crankcase by itself, but I would have thought it could when the crankcase is as full as you describe.

How this can be checked is also described in the workshop manual.

Search these forums for the link to Christians Archives all the information you need is there.Edited by - Eric on 03 Jan 2011 5:42:33 PM

iandusud · Post by **iandusud** » Mon Jan 03, 2011 5:52 pm

Hi Eric, thanks for your reply. I've sorted it. I pulled the pump and inspected the gaskets, drillings etc - no problems there. I then dismantled the bleed valve and found the ball to be stuck on its seat. Once I got it out I could see where it had stuck. Cleaned everything up and replaced the ball and bingo!

Cheers, Ian