Twin carb set up

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Andy G
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Joined: Mon Jun 01, 2020 9:42 am
Location: Aberdeenshire UK

Twin carb set up

Post by Andy G »

Been fettling my old dad's '60 31csr which is set up with twin carbs.
Was surprised to find that of the two Amal 389s, only one has a float and an extended chamber that serves both carbs. The second doesn't have any functional innards in the float chamber at all!

Is this normal or did he build an oddity?

I recall it running just fine btw.
Last edited by Andy G on Sun Oct 17, 2021 12:14 pm, edited 1 time in total.
Bombling contentedly around rural Aberdeenshire
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ajscomboman
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Location: HAMPSHIRE UK

Re: Twin carb set up

Post by ajscomboman »

Its a chopped Monobloc and perfectly normal.
Andy G
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Location: Aberdeenshire UK

Re: Twin carb set up

Post by Andy G »

Thanks Rob, had me scratching my head a while!
Bombling contentedly around rural Aberdeenshire
Groily
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Re: Twin carb set up

Post by Groily »

ajscomboman wrote: Sat Oct 16, 2021 7:25 pm Its a chopped Monobloc and perfectly normal.
Having had two - and still having one (a Notrun) - machine with this set-up, I'd agree they are fine.
But now and then I have found that a hot engine doesn't like being parked briefly on the side stand: seems to mess up fuel levels and makes hot re-starting harder than the usual first or second kick.

I was once told by a bar-room pundit that a conversion from bottom feed on the rh carb is possible, by modding the sideplate on the floatless carb and feeding the juice across through that. There may be some logic in it but I have never tried because using centre stands I've never had the problem. I'd be interested to hear if anyone else has been there?
Mick D
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Location: Aberdeenshire

Re: Twin carb set up

Post by Mick D »

Hi Andy

Burlen will supply a new set made to order if you need one.

Regards Mick
Andy G
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Posts: 358
Joined: Mon Jun 01, 2020 9:42 am
Location: Aberdeenshire UK

Re: Twin carb set up

Post by Andy G »

Time will tell Mick, but I'll take note of steer in case needed later.
I only get short opportunities to do any work on the bike which is at the otther end of the country so it'll be a while before I try to start it.
It was my dad's first rebuild after decades without bikes (national service, marriage and family conspiring against his younger two wheeled days). And it was a thing of beauty back then, sadly now much spoiled by a lack of attention since he passed.
So I'm "following the river" from tank to carbs, then heads and so on. Hopefully bring it back to a condition that does justice to his build.
Bombling contentedly around rural Aberdeenshire
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