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Matchless G12 oil pump #737797
06/05/18 10:06 pm
06/05/18 10:06 pm
Joined: Feb 2018
Posts: 26
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WilliamLangton Offline OP
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HI all. My 60 G12 is wet sumping something fierce, and rather than tap the feed line, I think it would be wise to change the oil pump. Also, just reading the factory manual, and it states that the main cause of oil leaking from the crankcase into the chain case is a deranged crankcase relief valve. Anyone familiar with this? This bike leaks oil profusely into the chain case. Also, this bike sat for almost 20 years. She runs strong, but the leak makes it impossible to ride ? Any tips?? Thanks in advance.
William

Last edited by WilliamLangton; 06/05/18 10:17 pm.

william langton mccormick
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Re: Matchless G12 oil pump [Re: WilliamLangton] #737818
06/06/18 2:04 am
06/06/18 2:04 am
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Posts: 2,122
Oztralia
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Rohan Offline
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Rohan  Offline
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Until you sort the oil leaking down, impossible to say if the relief valve is 'deranged'.

Remove the sump plug when you park it, and arrange a drip tray/tin underneath,
and see how much drains down overnight.
Note that you might get a bit of a gusher when you remove the sump plug too, so be prepared.

I'm not familiar with G12 oil pumps, but Norton pumps can be dismantled and the surfaces ground down flat on a sheet of wet-n-dry. This can make quite a difference.

Also, is this actually causing a problem when you ride it.
If its just when parked, you can always drain the sump before riding,
and if the oil is still clean just tip it back into the oil tank.
Always check the oil tank level AFTER doing this, before riding.
Ain't old bikes fun !

Re: Matchless G12 oil pump [Re: WilliamLangton] #737820
06/06/18 2:20 am
06/06/18 2:20 am
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Posts: 1,537
OZ
Triless Offline
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William, my experience with the AMC twins is minimal, " Matchless Twin Motorcyles" by FW Neill, first published 1957, has useful lubrication information. If you have an email address, I could send excerpts which I think may be of help, in conjunction with information you already have.
I would hazard a guess and say you may have a problem with oil draining from the tank into the sump when the machine is stationary. Neill states that if this fault develops when the machine had been stationary for a short period, check the non return valve at the end of the filter compartment in the crankcase for dirt under the ball seating.
He goes on to say in the case of a machine that has covered a great mileage, the fault may be due to wear in the spindle holes in the feed pump plate !
Excess oil in the crankcase would find its way into the chaincase via the breather!
Phil Walker was a development engineer under Bert Collier at AMC before WW2. Post war, he became a designer in his own right. The vertical twins were his work, as was the lightweight 250 and 350 singles, whose cylindrical gear box casings gave a quasi unit construction look. The primary chain was adjusted by revolving the gearbox in its mountings !

Last edited by Triless; 06/06/18 2:47 am. Reason: spelling
Re: Matchless G12 oil pump [Re: WilliamLangton] #737825
06/06/18 3:01 am
06/06/18 3:01 am
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Posts: 328
Irene, South Africa
robcurrie Offline
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Irene, South Africa
I just make sure I run mine once a week to pump the oil out the crankcase back to the tank. If left too long, the crankcase overflows into the primary and this has to be drained back to the correct level - this is also the reason to use the same oil in the engine and primary drive.

Rob C

The crankcase vent valve in the nut on the crankshaft is so simple that I doubt if it could be faulty - its just a loose disc that works like a reed valve.

Last edited by robcurrie; 06/06/18 3:07 am. Reason: Added comment on vent valve.
Re: Matchless G12 oil pump [Re: Rohan] #737834
06/06/18 6:45 am
06/06/18 6:45 am
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WilliamLangton Offline OP
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Rob,
Thanks for the reply. The info I have is direct from the factory manual. It states that the crank case vent valve is the primary cause of leakage into the chain case. Can you tell me where this valve is?

Much appreciated,
William


william langton mccormick
Re: Matchless G12 oil pump [Re: Triless] #737836
06/06/18 6:49 am
06/06/18 6:49 am
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Posts: 26
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WilliamLangton Offline OP
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Your knowledge is amazing, and much appreciated. Where can I find the non return valve? This machine will dump the entire contents of its oil within two weeks.

William


william langton mccormick
Re: Matchless G12 oil pump [Re: WilliamLangton] #737844
06/06/18 9:15 am
06/06/18 9:15 am
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Posts: 2,122
Oztralia
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Rohan Offline
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If Rob is starting his bike every week to prevent the sump/chaincase from filling, then he is in the same boat as you !!?

Reading online, these engines have a tunnel and a gauze/felt that is part of the oil filtering system. The non-return valve is to prevent all the oil in the filter from draining out and into the sump. So your manual should go into some detail about how to access the filter and non return valve. I'd imagine it would have to be in the timing cover ?

The singles are so simple, with the filter in the oil tank.
But I guess that only filters what is coming back out of the engine...

Re: Matchless G12 oil pump [Re: WilliamLangton] #737846
06/06/18 10:08 am
06/06/18 10:08 am
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Triless Offline
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This valve is incorporated into the end of the pressure relief valve, which is located in the lefthand cranckase, towards the front. ( a plug behind this, closer to the cylinder, is the cap for the oil distributor bush at the end of the exhaust camshaft ). Actually, have you access to a diagram of the oiling system to look at.
To be honest, my knowledge isn't amazing at all, really. I own only one Matchless, have so for 48 years, and have much interest in Matchless products, plus I am an avid reader. I was told once that really knowledgeable people have it all in their heads, at total recall. Dumb buggers have many books. I have quite a few books !

Re: Matchless G12 oil pump [Re: Rohan] #737847
06/06/18 10:15 am
06/06/18 10:15 am
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Triless Offline
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Rohan, as a matter of interest, my 1932 Matchless Bigtwin has the same filtration system as the postwar singles regarding the fabric filter in the return circuit, plus a gauze filter that sits under the oil filler cap that the oil discharges into after going through the fabric filter. And there is another courser gauze filter on the oil feed union in the oil tank.

Re: Matchless G12 oil pump [Re: WilliamLangton] #737886
06/06/18 8:40 pm
06/06/18 8:40 pm
Joined: Mar 2013
Posts: 328
Irene, South Africa
robcurrie Offline
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The valve in the oil filter gallery is a bypass valve, the check valve should be in the oil pump mounting plate and the breather valve is in the nut on the left-hand end of the crank. The check valve position could be different depending on year. The oil that ends up in the primary overflows through the main roller bearing. There was an aftermarket mod made to the oil pump (oil drains through the return pump from the oil tank) which provided o-rings in the pump end plates to stop oil passing through the spindle holes, but I think the oil mostly leaks past the gears, check that the end plates are free of scoring. The return pump is the rear unit and should be the larger of the two pumps, don't mix parts from different pumps.

Rob C

Re: Matchless G12 oil pump [Re: robcurrie] #737897
06/06/18 10:06 pm
06/06/18 10:06 pm
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Triless Offline
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Rob, as I understand it, the check valve in the oil pump assembly is on the return pump ( towards rear of engine ), and the purpose of this is to keep the return gear pump "wet" when engine is not running. With the diagrams I have, the oil pressure relief valve, and a non return valve, are a combined unit in what also serves as the oil filter removable end cap, located towards the front LH crankcase. This is for the G9 and G11, so maybe different for G12. Although, I'm positive there weren't major changes to the oiling system !
I have found out that in 1956 the "two piece " oil filter end cap unit was changed from two piece to one piece to obviate mixing the two different springs involved, and the non return valve for the filter unit was now a sealed unit (P/N 023331) . The G12 was introduced in 1959.

Last edited by Triless; 06/06/18 10:43 pm. Reason: addition
Re: Matchless G12 oil pump [Re: Triless] #738019
06/08/18 1:29 am
06/08/18 1:29 am
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WilliamLangton Offline OP
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Triless,
Thank you so much. This valve is horizontal or vertical?

W


william langton mccormick
Re: Matchless G12 oil pump [Re: robcurrie] #738020
06/08/18 1:30 am
06/08/18 1:30 am
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WilliamLangton Offline OP
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Rob,
Thank you so much. I will go after the valve first.
W


william langton mccormick
Re: Matchless G12 oil pump [Re: Triless] #738021
06/08/18 1:32 am
06/08/18 1:32 am
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WilliamLangton Offline OP
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Did we ever determine the correct location of the valve?


william langton mccormick
Re: Matchless G12 oil pump [Re: WilliamLangton] #738029
06/08/18 2:44 am
06/08/18 2:44 am
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Triless Offline
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William, the valve is located towards the front on the Left Hand ( Driveside) crankcase. It is to the front ,on a horizontal plane, and a bit lower, than the exhaust cam end plug ( just to the front of the cylinder assembly )which accesses the the oil distributor for the top end. Don't touch that cap.
I'm sorry if I'm not explaining things too well, I'd feel much happier if you could access the relevant diagrams of the oiling system ! Hopefully, somebody will come along with more practical experience, theory is good to a point ! The minimal experience I had with a G12 was many years ago, and the atrocities that had been inflicted on that engine previously was beyond belief !

Re: Matchless G12 oil pump [Re: Triless] #738389
06/11/18 5:00 pm
06/11/18 5:00 pm
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WilliamLangton Offline OP
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Triless,
I removed the valve and gave it a good clean. It was not stuck, but oddly, since I bought this bike a few months ago, the crankcase has contained oil that seems water contaminated--milky brown. I am assuming the previous owner may have somehow gotten water in it, as I cannot explain this otherwise. Perhaps this bad oil is contributing to my profuse leak. Not only does the chaincase fill, but it then leaks, even though I resealed it w a fresh gasket. Very frustrating.


william langton mccormick
Re: Matchless G12 oil pump [Re: WilliamLangton] #738396
06/11/18 5:43 pm
06/11/18 5:43 pm
Joined: Mar 2013
Posts: 328
Irene, South Africa
robcurrie Offline
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If the chaincase fills, it will leak out the breather hole (near the alternator harness hole) and the gearbox shaft hole behind the clutch. The oil level should be just touching the primary chain. Make sure the surfaces of the chaincase are flat, paying attention to the threaded holes which can be countersunk lightly in case the threads have pulled slightly. The large gasket can also shrink when left open for a long period, so make sure there is still contact all round. There should also be a gasket between the crankcase and chaincase.

Rob C

Last edited by robcurrie; 06/11/18 5:44 pm. Reason: spelling
Re: Matchless G12 oil pump [Re: robcurrie] #738397
06/11/18 5:47 pm
06/11/18 5:47 pm
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WilliamLangton Offline OP
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Rob,
Thanks for that tip on the threads. I already replaced that large gasket--and I saw that breather hole you are referring to. I just wish I knew why it was leaking. Are new oil pumps even available?

Thanks again,
W


william langton mccormick
Re: Matchless G12 oil pump [Re: WilliamLangton] #738410
06/11/18 7:07 pm
06/11/18 7:07 pm
Joined: Mar 2013
Posts: 328
Irene, South Africa
robcurrie Offline
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You won't find new pumps, but you could scour the web for good used ones. I remember reading an article by a member of the Jampot club who retrofitted more modern pumps (I think from a Triumph) to his AJS, he made a new pump mounting plate that connected the channels correctly without modifying the engine at all. I will have a look if I can find it.

Rob C

I found the info, Google search for"Jorg Henze Morgo pump"
He wrote an article in the "Tech Tips" section on the Jampot website - only available to members.

Here is an old discussion on the forum:
http://www.jampot.com/forum/viewtopic.php?f=20&t=6942&hilit=jorg+henze

Last edited by robcurrie; 06/11/18 7:48 pm. Reason: spelling - again and additional info
Re: Matchless G12 oil pump [Re: robcurrie] #738426
06/11/18 9:36 pm
06/11/18 9:36 pm
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Posts: 26
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WilliamLangton Offline OP
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Rob,
Thanks so much. BTW, if my issue is in fact the pump, what exactly in the pump is the cause of the drain-off? If I can isolate the component, perhaps I can repair it.

Much appreciated,
W


william langton mccormick

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