AJS & Matchless Owners Club

Have a newly rebuilt 55 G9. Only had it running once. Oil return was fine. Then it stood for six weeks and now I found basically the whole oil content had gone into the engine oil sump. The little plunger and spring held by the register cover is in place. Any clues to what's wrong?

There's probably nothing wrong except general wear in the gears, spindles and plates in the oilpump. Gear pumps have to have some clearance so oil will seep through them even when new. Members have done various methods to prevent or slow it down. Some fit a tap in the feed, usually with a foolproof switch connected to the ignition or a long handle which the kickstart can't pass without turning it on. Some use SAE 50 oil which may help. Some fit small screw to the drain plug so that it doesn't wear the thread in the crankcase with repeated removal. The easiest way is to use the bike regularly or remember to start it up and run it for a few minutes once a week or so.
Dave

That much in six weeks? Hopla!

Posted a reply in your other thread, just nothing more than worm pumps if you didn't surface face the outer and rear plate. There's not much can be done with worn spindles other than an o-ring mod. Message me for more details otherwise the ads police will be onto me!!

I have most of the parts for a NOS oil pump. What's the correct axial play for the oil pump gears?

I don't think you'll find a figure for the amount of play. If you've got new end plates and gears there should be very little.
Dave

On my original and second hand one the gears were 0.0025” thinner than the centre pump plate and it felt like a lot of endfloat. So I’ve reduced the centre plate thickness until all the endfloat has gone, and this has raised the pressure a little.

I found a figure in the 'Tuning for speed' book. 0,001 end play recomended. Very handy book btw, not that I'm tuning for speed, but lot's of such small good hints in it.

magnusk750 wrote: ↑Sat Mar 30, 2024 10:00 pm That much in six weeks? Hopla!

I would agree tthe whole oil tank in 6 weeks does seem excessive. I think its worse if you put the bike on the side stand. I fitted a tap on mine linked to the mag. I know this is treating the symptom not the cause but it got worse when i started using 20/50.

An overlooked problem with wet sump is the non return valve at the end of the oil filter channel.When I refurbished my 1958 G11 I fitted a refurbished oil pump, with a cover and o-ring on the feed pump, after it had been standing for a while, a lot of oil had leaked into the sump. I removed the timing cover, and could confirm that no oil was coming from the oil pump in the timing side, so the only way to the sump was through the oil filter channel. I checked the so called non return valve and the oil could seep through it quite slowly so i ordered a new one from the club it was even more leaky, so i decided to take it apart to see if i could make it tight it was pretty easy to take it apart it was only assembled with 3 punches there was no seat at all for the ball so i decided to make a new isert with a proper seat, then the valve was oil tight and now the motorcycle can be left from October to March without wet sumping. In 1955 there is another type of non-return valve, the ball seat can be easily refreshed by unscrewing the screw at the end, perhaps the ball should also be changed
The non return valve is described in the books as a valve to prevent the oil from flowing back from the top end, but most of the oil in the top end flows into the crankcase through the push rod channels and the rest flows through the oil channels back to the distributor and from there to the main bearing, so I can only see that the function is to ensure that the oil during standstill does not flow from the filter channel down to the main bearing from where it ends up in the crankcase. hope you understand my english
Poul Denmark