1951 barrel on a 1954 18S ?

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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1951 barrel on a 1954 18S ?

Postby asterysk_usa » Sun Nov 10, 2019 4:34 am

Image

I checked the number against the spares database and 013792 is the part number for a 1951 barrel

The engine crankcase shows the engine is a 1954

Is this likely a replacement barrel or do you think they may have used old stock at the factory

Any suggestions how I find out the difference between this 013792 and the correct barrel 018169 ?

Thx


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1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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Re: 1951 barrel on a 1954 18S ?

Postby Reynard24 » Sun Nov 10, 2019 9:40 am

One difference would be that the fins are cut away on the '54 barrel to accommodate the SR1 magneto, clearance is very tight without this modification. The illustrated parts list does not show this unfortunately.

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Re: 1951 barrel on a 1954 18S ?

Postby asterysk_usa » Sun Nov 10, 2019 9:44 am

Reynard24 wrote:One difference would be that the fins are cut away on the '54 barrel to accommodate the SR1 magneto, clearance is very tight without this modification. The illustrated parts list does not show this unfortunately.


That probably explains why I have a non standard magneto !!
1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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Re: 1951 barrel on a 1954 18S ?

Postby SPRIDDLER » Sun Nov 10, 2019 10:12 am

asterysk_usa wrote: Is this likely a replacement barrel or do you think they may have used old stock at the factory

I reckon James has the answer.
It would be highly unlikely for the factory to have 3 year old stock of cylinders since for several years post-war the U.K. was virtually bankrupt and steel/iron was in short supply. (I understand that's why the Land Rover was designed with a mostly aluminium body).

I've read that the allocation of steel and iron was prioritised for manufacture of export products in order to obtain foreign currency. Although I don't think 500's were used by the military maybe there was a replacement '51 cylinder readily available in Cyprus?
Incidentally, 1951 was the year that the cylinder head material was changed from iron to aluminium (for performance reasons).
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Re: 1951 barrel on a 1954 18S ?

Postby Andy51 » Sun Nov 10, 2019 4:40 pm

I had just this problem on my '54 G80 a while back. It came with a Lucas N1 magneto to which the ATD had been fitted. I got the correct SR1 at a good price, so set out to fit it - it wouldn't quite fit however hard I tried. After much trying I realised I should have a barrel with cut away fins. I tried filing them in situ (don't go there!) but soon realised that too much metal needed removing - and why the PO had used the wrong mag. In the end I took the barrel, which by now I realised was an earlier one, to a local machine shop who put it on a mill and did the job in short order for a reasonable sum. I must have got the measurements for the cut away from someone in my local section, but can't remember now. The upshot is you need a cutaway barrel for the right (SR1) mag, or a wrong (N1) mag to go with your earlier, uncut, barrel. Cheers, Andy

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