AJS & Matchless Owners Club

Please help. I had no responses rom my first request in November.
My 1963, G12, 650 twin has a high capacity oil pump. The horizontal oil-way feeding the scavenging pump via a ball and spring valve is accessed from the bottom by a second drilling assembled with a strong spring and cup. I believe that this is for oil pressure relief. A third drilling accesses the second drilling and this I believes allows the oil to escape when the oil relief spring has been compressed sufficiently. This drilling has been blocked off and hence high pressure oil (130 p.s.i. on cold start) cannot escape. Is this correct, or should I remove the blockage. Any idea why it has been blocked in the first place?

The engine does not include such a device on the end of the filter tunnel, I am not confusing this with the single direction oil valve at the left hand end of the oil filter.

Hi Graham. First off I must say that I do not have an in depth experience of the G12 high capacity oil pump, however I do have a backplate for this pump.
As you say the drilling is blanked off. Investigation with an oil-can revealed that when the pressure relief valve lifts it connects the delivery side of the pump to the suction side, thus giving the required relief.

Graham

Alan is quite right, when the piston is forced off its seat by excess oil pressure the discharge port is connected to the suction port. I prepared a drawing to explain it to you better but there does not seem to be a facility for attatchments, and as you have no e-mail there seems no way to get it to you. Any way be sure to leave that blanking plug in place.

Laurie

Laurie, After my B52 clutch gaffe, see recent 'Jampots', its nice to know I have got something right!

Alan, Laurence. Many thanks for your information. I had tried looking for an alternative relief to the blanked drilling but could not see anything, perhaps its blocked? I will try the oil can method as Alan suggests. I will leave the blanking in on the second drilling.

Graham