AJS Model 18CS - unusual parts identification

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Cjay59_LAPSED
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Re: AJS Model 18CS - unusual parts identification

Post by Cjay59_LAPSED »

Hi Dixter,

thank you for your kind appreciation of my machine, doing a few things to it over the next few months so will post a few photo's later in the year. Hope your not getting frozen, some of the US seems to be arctic at the moment. Love the list of your stable of machines, sounds a bit "What's in the Barn".

The front is a Mitas Trials,
Front.jpg
The rear is a Dunlop Universal,
Rear.jpg
keep in touch, how you getting on with that G80L?
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SPRIDDLER
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Re: AJS Model 18CS - unusual parts identification

Post by SPRIDDLER »

Cjay59 wrote:I don't know where you found the date for the gearbox, ...........
Here's a source of dating info ...........

http://archives.jampot.dk/technical/Tra ... umbers.pdf
'There is a tide in the affairs of men
Which taken at the flood............'
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Cjay59_LAPSED
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Re: AJS Model 18CS - unusual parts identification

Post by Cjay59_LAPSED »

Spriddler, checked my gearbox to the list, '55' 20B, which was an export!!!! so interesting, thanks again...
Gearbox.jpg
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Mick D
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Re: AJS Model 18CS - unusual parts identification

Post by Mick D »

Hi

As an aside, does anyone know what the three digit number in the rectangle signifies? Would this be the inspector's stamp?

Regards Mick
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clive
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Re: AJS Model 18CS - unusual parts identification

Post by clive »

Mick D wrote:Hi

As an aside, does anyone know what the three digit number in the rectangle signifies? Would this be the inspector's stamp?

Regards Mick
can you see it anywhere else on the box? my guess would be its to keep the three parts of the box together once they have been machined for the shafts. I have seen similar 3 figure numbers stamped on a matched single crankcase and inner timing cover (underneath).
clive
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Mick D
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Re: AJS Model 18CS - unusual parts identification

Post by Mick D »

clive wrote:can you see it anywhere else on the box? my guess would be its to keep the three parts of the box together once they have been machined for the shafts
Hi

That's an interesting thought :beer: - I've not noticed the stamp anywhere else yet but neither have I fully cleaned the components of my gearboxes.

Each box seems to show evidence of a similar mark in the same area:
Inspector 1.png
Inspector 2.png
Regards Mick
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clive
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Re: AJS Model 18CS - unusual parts identification

Post by clive »

Next thought is that the number may identify the worker who assembled the box in the event there was a problem when it was fitted to the motorcycle and perhaps rejected by the manufacturer. With the little oblong round the number it does not look like individual number stamps were used. The worker may have had their own three number stamp. As you say though it could be an inspectors stamp after the function of the kickstart and gearchange were quality tested.
clive
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Feral
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Re: AJS Model 18CS - unusual parts identification

Post by Feral »

Cjay59 wrote:I wouldn't trust your engine stamps, they don't look right I'm sorry to say, but others here will have more experience and I would hope others will comment. But mine is also not a competition engine, and I don't mind. The alloy Wellworthy barrel reduces weight and centre of gravity. I want mine as a road bike, an Enduro basically so having a lighter road geared bike, styled the way I like is better than a true Trials or Competition machine, so I think it all depends on what ultimately you want to do with your machine. As a true CS holds a premium value, there will always be people who will try and forge them.

I agree the C.1 does look original, but sorry, I don't know what it means.

If the engine was a true competition engine I would be surprised if someone re-stamped it, others may know of differences that could tell you if it was a comp engine.

I don't know where you found the date for the gearbox, as I understand it the 52 stands for it's introduction year, 1952, they came in road ratio, close ratio and trials ratio, and they were used by AMC from 1952 to 1956, the trials until 1955. Post a photo of the stamp and should be able to tell your more.
Hi Cjay,

I don't care about the numbers on the crank case, it is the components that the engine is made of that matter to me, as they are the bits that make it go, numbers just make identification easier.

Other than a competition head and barrel, was there any difference in a competition engine?

I have checked gearbox the numbers against the list that you posted and guess what? It isn't listed. Pretty sure that it is a Burman from 1948 (From the pictures that I have seen, the front cover is as fitted to 48 models), but the rest is a mystery.

Number G24 C 48
AJS Model 18 gearbox resized 2.jpg
As regards what I want to do with the bike, the first thing is to get it all working as it should and then stick some lights on it, I already have a reconditioned dynamo, but nothing else. It will be for road/dirt track use, so finding out the gearing is pretty crucial.

I have just acquired a G9 engine which is more in keeping with the frame's roots, so that is an option. For now though, I like the way that it looks with it's age showing and being a bit shabby.

Cheers John
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clive
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Re: AJS Model 18CS - unusual parts identification

Post by clive »

"It will be for road/dirt track use, so finding out the gearing is pretty crucial."

That certainly looks like a Burman CP box. They did make gears for trials that were lower one to three and then a jump to fourth. Required them to be replaced as a set mainshaft and layshaft gears, not many around although I sold a genuine box with the trials gearing about 3 years ago so they do occasional appear. Only way you are going to tell what the gearing you have is to dismantle it and count the teeth.

You can adjust the final ratio by playing with the number of teeth on the gearbox sprocket if you have a standard road box. The other option is to change the engine sprocket for a lower number of teeth. The standard road sprocket is 21 (on the larger primary chain sprocket) for a road 500. The 350 has 18 teeth so there are lots of these around, and they did make sprockets down as low as 15 but these are hard to find and would not be needed on your 500.
clive
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Re: AJS Model 18CS - unusual parts identification

Post by Cjay59_LAPSED »

Hi John,

Clive has mentioned the studs earlier, in Roy Bacon's book he says, "In 1951 the compression plate on the 500 was removed on the road model and the barrel lengthened to compensate, so that seekers of a higher ratio had to fit another piston. The competition units retained the plate which served as an easy means of changing the ratio to suit trials or scrambles", also in 1956, "The 16MS and 18CS/G80CS were fitted with all-alloy short stroke engines".

I have similar questions over my engine and gearbox, the person who worked on it is no longer alive so I'm not sure yet of the internal gearing or what has been done to the pistons etc, so it's anyone guess as to what may have be changed, or not!

So as you, I want a good working all rounder, which is fun to ride, and if it doesn't perform the way I want, then I will look at the gearing, at the compression ratio, etc.

I am in the process of fitting lights, mine has a full loss system, a battery under the seat that I remove and recharge as needed. Rob H had posted up the Lucas parts list,
Lucas MU42.jpg
MU42 1956 AJS 18CS.png
I found this one to install,
MU42.jpg
it will need some work to get it how I want, but should be fun, I have bought some fork ears to put on and a fork puller to take them apart, the fork puller comes with two threads so I will find out which forks I have when I do it.

I asked what you wanted to use it for because if you wanted a bike to thrash around a field, then the stamping as you say doesn't matter, if you wanted to do a full restoration, it might not be the bike to use, what you use it for, is what its about. Mines a bitsa and I don't care, its only an old bike and I'll adapt it to suit me and if it gets a bit old and shabby, even better.
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