Amal 389 jetting

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Re: Amal 389 jetting

Postby ajscomboman » Tue Apr 18, 2017 8:39 pm

The monobloc will be fine and the link Stuart posted is to the 56 owners manual. You my have to play with the main jet and needle settings to get it spot on. As a guide the early 55 500 singles used a 240 main and the needle in the second from top notch, 56 models used 270 main needle in the centre notch. Forget about the numbers stamped on the carb as they will probably no longer be relevant. The number after the 389 stamping relates to the Amal code that the carb was jetted to to fit a specific make/model.

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Re: Amal 389 jetting

Postby Rob Harknett » Tue Apr 18, 2017 9:06 pm

Steve Harding wrote:Thanks for your help

http://archives.jampot.dk/technical/Car ... 54_AMC.pdf
All the info there now, carb type all the jet sizes etc etc. ( AMC only )
As Rob says you do need to play with jets sizes etc. Modern fuel could also mean changing what was once correct for the fuel at the time,
You will now see in the file just archived, the old original carb bore size. Which differs from what you now have fitted.

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Re: Amal 389 jetting

Postby raffles » Wed Apr 19, 2017 6:59 pm

The 389 that you have will serve you well the 27 main jet is correct 260 is for carb fitted with air filter carb bore sizes will make little difference
as long as its around 1/1/8th needle position in the middle pilot jet air screw one and one half turns out.
Tony

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Re: Amal 389 jetting

Postby Steve Harding » Wed Apr 19, 2017 10:25 pm

Thanks all. parts ordered

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