Please clarify re oil in the combustion chamber

Information relating to the Matchless G9 or AJS Model 20 500cc twin
zwarts
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Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Please clarify re oil in the combustion chamber

Post by zwarts »

If you find that there is no breather at all due to this combination of crank/cases, one solution is to fit a breather on the timing cover. I can send photos of how to do this if necessary.
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clive
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Location: LONDON UK

Re: Please clarify re oil in the combustion chamber

Post by clive »

Carson wrote:Thanks Duncan, I guess it is pretty clear that I have the part #011648 breather, God only knows why that is on cases marked 1954, some weird things happen to machinery over time. Looks like you would have to dismantle the clutch etc to pull that breather out for a look-see. Not going to happen, at least no now. I will have to assume it is working, and you know what happens when you assume something.
Clive, would love to attach a photo but my computer skills have not improved passed regular typing so in short I don't know how.
Carson i think you are rapidly in danger of experiencing even more frustration. Part 011648 is NOT the breather. It is simply the cover for the inlet camshaft tunnel. The holes you can see are actually just blind drillings to allow a special tool to be used to tighten up the cover. The breather is made up of two parts 014248 and 014917 illustrated earlier in the thread. By 1954 they had moved to venting the crankcase through the drive shaft as previously described and they simply left part number 014248, which you cannot see, out. They did however fit part number 001648 as it is simply the cover for the tunnel.
The only point in taking your clutch and primary chaincase off to undo this item would be if you had part number 014917 fitted to your crankcase. I imagine your crankcase will not have the drilling or thread for this second part. This would be visible and was fitted in the threaded hole just above the engine mounting and behind the camshaft tunnel in the illustration. Unless you have BOTH parts you do not have the earlier engine breather. Hence my suggestion of a photo.
If you do not have the second part mounted on your crankcase, there is little point in undoing the clutch as whether or not you have part number 014248 behind it , there cannot be any venting going on. You would be better advised to move to immediately fit the breather to the timing cover as suggested by "Zwarts". An advantage of this would be that if you ever installed the correct later crankshaft you could purchase another timing side cover and be back to original. Meanwhile you can fit the breather to the timing cover which is easily removeable. A further word of warning if you have the correct timing side cover there will be a spring behind it near the dynamo. This operates the oil pressure relief valve (for when the oil is cold) and can easily fall/spring out as you take the cover off.
Good luck you will probably need more of the whiskey.
clive
if it ain't broke don't fix
Carson
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Re: Please clarify re oil in the combustion chamber

Post by Carson »

Zwarts, would very much appreciated if you could send photos, I don't know if it has to go through the club site or can you send them to my email address....carjak@shaw.ca
Clive, once again your response is very informative and appreciated.

Carson
ajsph
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Location: DENMARK

Re: Please clarify re oil in the combustion chamber

Post by ajsph »

in the attached pictures you can see the difference between the Crankcases before 52 and after 52
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Carson
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Location: British Columbia Canada

Re: Please clarify re oil in the combustion chamber

Post by Carson »

Well, I guess I was the victim of a fraud? AMC tells me that motor (sent him photos) is a 50/51 so someone re-stamped the casings. I did a frame number check on the dating service and it comes back as a 54 frame. Not sure what I will do now, definitely will require more whiskey and perhaps a lawyer (yea right!)

Carson
zwarts
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Location: LANCASHIRE UK

Re: Please clarify re oil in the combustion chamber

Post by zwarts »

Zwarts, would very much appreciated if you could send photos, I don't know if it has to go through the club site or can you send them to my email address....carjak@shaw.ca
Email with photos sent - Sorry, I don't know how to post photos on here!
craigcc
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Joined: Wed Oct 03, 2012 10:15 am
Location: CORNWALL UK

Re: Please clarify re oil in the combustion chamber

Post by craigcc »

Bags of good advice and checks from various members in my first thread on this. Not solved the problem though - but do go through the thread to eliminate other potential factors.

Sounds like we have a similar problem - mine's a 1953 bike. I'm tearing my hair out.

Craig.
Groily
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Re: Please clarify re oil in the combustion chamber

Post by Groily »

Regardless of all the discussion on the lubrication system . . . (and apologies if you've covered what I'm about to say several pages ago, or if I've said it before and you've ruled it out) . . . have you looked at the pistons really closely to see that the rings are not too thin for the grooves?
If they have up and down movement (forget 'TOP' and all that, forget the gaps, and forget basic bore diameter), they WILL act as pumps and you WILL get oil pooling on the piston tops. It is all too easy - I've done it on my '54 and scratched head and got splinters for ages - to use rings that are a 32nd or something too narrow for the grooves in up and down terms. Result, huge amounts of oil on top, then oozing out of the exhaust, smoke everywhere. Very effective little pumps they can make. My problem was using rings designed for pistons other than the ones I fitted (for wire-wounds not for Hepolites/AEs or vice versa or something), and not spotting that there were these small differences.
Metering jets, other oil system bits, breathers and the rest of it can all play a part, make things smoke, mess up the circulation, etc etc - but the only time in 40 years I've ever had real puddles of slime such as you describe was due to mismatched compression rings/pistons.
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1608
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Re: Please clarify re oil in the combustion chamber

Post by 1608 »

Ill fitting rings in the piston groove is a well known case of pumping oil into the combustion chamber. If the rings came with or are matched correctly with the pistons then thats not the problem. Idealy the gap btn ring and groove should be about 2thou, max 3thou.
I still get oil pooling on my piston tops after something like 5 or 6,ooo miles, but it doesn't smoke.
I found fitting oil metering plugs in the heads helped. These plugs were omitted in 1960 but re-introduced in 1962. AMC never seem to have got to grips with the oil system on the twins.
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