Oil system 1960 M20

Information relating to the Matchless G9 or AJS Model 20 500cc twin
leswaller
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Re: Oil system 1960 M20

Post by leswaller »

REW wrote:May be a little early in the rebuild to ask this, but it also relates to oil changes on a twin. Once drained and filters replaced and oil tank filled, does one just start up and hope the new oil quickly fills the various spaces now air filled? Can all the air be purged before the initial start up? What do the experts do?
Assuming you have put plenty of oil on the various parts whilst reassembling and also soaked the filter with oil, the best way is to take the plugs out and spend 5 minutes cranking the engine over by hand (or foot). After that when you start up you should find it will only be a few seconds before the pump is squirting oil back into the tank
Les
Rules are for the obedience of fools and the guidance of the wise
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Rob Harknett
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Re: Oil system 1960 M20

Post by Rob Harknett »

I have only ever drained and refilled, then started the engine. The pump will build up pressure and start circulating oil, building up correct levels of oil in various places in the engine, until it starts to return. All explained in the workshop manual. Oil will replace air. Putting oil in various pipes may result in an air lock. Think how you fill your car with water. You remove the upper most pipe in the system. Slowly fill with the rad. with water until it emerges at the top pipe removed. The system is now full with no airlocks. Fill with water without doing this, you may note a rapid fall in water level due to airlocks, or you may not loose the air locks and overheat the engine. Water or oil may not circulate, if water or oil is blocking the passage of escaping air. Can it. ???? After a few minutes you should see spurts of oil/air escaping, followed by just an oil return. Your system should now be at correct levels in the engine. Good reading here.
http://archives.jampot.dk/book/Workshop ... .NEILL.pdf
Start at page 7 of the book ( no. 4. on the PDF file page counter. ) it is followed by faults to investigate should oil not return after a few minutes of the engine running. Those few minutes may seem long while you wait and watch for the air to escape and oil return to the tank. Theres many spaces to fill that need to trap oil. Same methods apply with your central heating. You undo the top of the rad. for air to escape , followed by spurts of air and water until all air has been expelled. Failure to allow air to escape will result in an airlock.
Mick D
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Re: Oil system 1960 M20

Post by Mick D »

Hi

Filling an oil line that is intended to pass oil won't result in an airlock - filling an oil filter with oil on installation is good practice - the more oil you can get into an oil system after maintenance the better, it will reduce the time to achieve designed circulation.

Oil systems on these machines, (and most others), are self bleeding - priming oil systems is good and accepted practice.

I'm sure that filling the oil tank and waiting will work, but I prime everywhere possible in the knowledge it will do no harm and will probably be beneficial.

Regards Mick
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Cliff-1959
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Re: Oil system 1960 M20

Post by Cliff-1959 »

All useful advice above, thanks chaps.

I am giving everything a good clean at the moment, and generally checking components before the rebuild. I am having trouble understanding how the oil distributor works. I can see how it is driven off the exhaust camshaft, and held in place with the external chromed nut. But I can't see how it pumps oil up to the rockers and valves. It just looks like a plain round disk with a threaded hole in the centre. I have looked in the manual and parts list and I can't see any other components, so what is the threaded hole for? All I can think of is to attach a small bolt to act as a puller to remove it.
Plodding along ...
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Duncan
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Re: Oil system 1960 M20

Post by Duncan »

When assembling I always use graphogen to prevent wear until the oil makes its way around.
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Rob Harknett
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Re: Oil system 1960 M20

Post by Rob Harknett »

I tend to go by the book. Can you think of any reason why priming the oil pump engine is not mentioned or even hinted as being an advantage? Could be because it could hide an oil circulation fault, you would had discover sooner than later. Letting the engine do its job satisfactory should prove the oil circulation is working OK. Finding out while riding it may prove too late. I have now been riding AMC bikes, by the book for 60 years. Never had an oil circulation problem yet.
Mick D
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Re: Oil system 1960 M20

Post by Mick D »

Hi Rob

Your book would appear to be 60+ years old - it obviously works for you but that shouldn't prevent others from moving on in line with current technology / thinking.

Regards Mick
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1608
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Re: Oil system 1960 M20

Post by 1608 »

give the oil filter a good soaking, and put about 1/2 pint of oil into the sump via the push-rods. The oil distributer does not pump oil, it simply regulates it to the top end. This is achieved by a small drilling in the older style drums and a flat on the improved later ones. If the alloy drum is badly scored then its worth replacing, not expensive.
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REW
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Re: Oil system 1960 M20

Post by REW »

To conclude my oil change question, thanks for all the replies and suggestions which I have combined and tried out. Filters soaked, oil lines filled, engine cranked about 100 times with plugs out. The oil bubbles and circulates, apparent firstly at the return union with the crankcase if you leave it slightly open and shortly afterwards in the tank's filter tunnel. Tighten everything, plugs in, swing and... bingo. Oil splutters immediately and after a few burps and farts trickles back as per usual.

I have no doubt such care is not essential, it may not even be useful Rob, but I don't half feel better for taking the trouble. It's the first time I have worked on a twin and I have learned a fair bit.
Ron

1951 Matchless G3L thumping round the Durham Dales.
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Cliff-1959
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Re: Oil system 1960 M20

Post by Cliff-1959 »

I spent a lot of time kicking it over with the plugs out too. It seems like logical, good advice. It started after about three kicks, so I was very happy with that, and the old return started quite quickly. Ive done a few hundred miles now and it is running really sweet. BUT, I am going to be changing the oil very frequently. The clutch seems heavier than I remember, so I think that I might have tightened the clutch springs too much, does anyone know how you should tension them?
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