Ebay motor

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Ebay motor

Postby Sykes » Tue Jan 22, 2019 10:28 am

I managed to pick up this little beauty on ebay.

Was there ever an alloy barrel made for the long stroke motor?
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Re: Ebay motor

Postby raffles » Tue Jan 22, 2019 8:01 pm

Yes there was an alloy barrel made by Allfin it fits most longsrokes if you can find one they all seem to be fitted
to made up trials bikes. By the way your engine was originally all iron
Tony

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Re: Ebay motor

Postby raffles » Tue Jan 22, 2019 8:06 pm

Just remembered ALLFIN barrels were made by WELLWORTHY
Tony

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Re: Ebay motor

Postby SPRIDDLER » Tue Jan 22, 2019 8:14 pm

WellworthyCylinders (640x576).jpg
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Re: Ebay motor

Postby Andy51 » Tue Jan 22, 2019 8:23 pm

The G80CS up to 1956 was long stroke and had an alloy barrel. Post '56 are short stroke. The alloy barrels on comp models use through bolts from crankcase to head, and hole spacing does not match standard alloy heads; it would be a major engineering job to fit alloy barrel and standard head together. An alloy barrel using standard flange fittings was made for the 350 on, I believe, Dutch Army request. Steve Surbey used to list them on his website years ago, but I doubt he has any now. Only a couple of hundred 500 CS were ever made and the chances of finding a 500 long stroke alloy barrel are probably less than winning the lottery - I have been looking without success for many years! I saw one on US ebay many years ago and it went for a very large sum. Cheers, Andy

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Re: Ebay motor

Postby raffles » Tue Jan 22, 2019 8:35 pm

As I understand it the Alfin barrel was to be fitted to the standard engine not the comp one
Tony

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Re: Ebay motor

Postby Andy51 » Wed Jan 23, 2019 9:32 am

Only the 350 - as I understand it, the Dutch Army, who used G3's, asked for a lighter machine and a number of alloy barrels were made for them. I don't know if the Dutch ever bought many or made them standard issue, but a few made it on to the UK market - the alloy barrels may even have been a non-works private venture - anyone out there know more on this story? Replicating the iron barrel flange fitting in alloy was OK for a 350 which has more 'meat' around the cylinder base and in low state of tune, alloy was strong enough for this. Also, it had to be a one for one replacement for its intended market. A flange in alloy for the 500 which has less meat around the cylinder base would not be strong enough, especially as the main market would have been scrambles machines in a higher state of tune, hence through bolts. No idea why they went for different bolt hole placing - goes back into the mists of time! Cheers, Andy

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Re: Ebay motor

Postby ajscomboman » Wed Jan 23, 2019 7:53 pm

Andy51 wrote:The G80CS up to 1956 was long stroke and had an alloy barrel. Post '56 are short stroke. The alloy barrels on comp models use through bolts from crankcase to head, and hole spacing does not match standard alloy heads; it would be a major engineering job to fit alloy barrel and standard head together. An alloy barrel using standard flange fittings was made for the 350 on, I believe, Dutch Army request. Steve Surbey used to list them on his website years ago, but I doubt he has any now. Only a couple of hundred 500 CS were ever made and the chances of finding a 500 long stroke alloy barrel are probably less than winning the lottery - I have been looking without success for many years! I saw one on US ebay many years ago and it went for a very large sum. Cheers, Andy


Tut tut Andy, I'm sure you meant up to 1955 as 56 was the first of the shortstroke models.

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Re: Ebay motor

Postby Cjay59 » Tue Jan 29, 2019 12:51 pm

I'm confused, I understand my engine to be a 500cc 1953 with an AL FIN alloy barrel long-stroke?

Does mine have an alloy head and alterations to fit it?

It could be Trials tuned, at this point I don't know, any help here would be appreciated!

As Tony says "a made up" Trials bike, supporting his point, alloy barrel on standard engine 18s.

And what is the "B" stamped on Sykes engine mean?

So many questions.......!!!

AJS AL FIN 500cc 1952 001.jpg


AJS AL FIN 500cc 1952 002.jpg


AJS AL FIN 500cc 1952 003.jpg
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Re: Ebay motor

Postby clive » Tue Jan 29, 2019 1:09 pm

Cjay59 Your cylinder head appears to be ally. Easy test though if it is an iron head a magnet will stick to it.
clive
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