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Mk1 Amal Settings For A Bsa B40..


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I recently bought a BSA b40 trials bike "SS engine,distributer type it has Boyer electronic ignition fitted and came with a mk1 Amal carb which i think needs setting up proper, as it wont rev out and it backfires and spits the occasional flame,

The plug shows heavy black deposits,

I noticed tonight that the front pipe is going a bit purple colored.

The carb has 622 with a 4 manually stamped over the last 2, making it 624,

I measured the in and out at 24mm and the slide tube at 30mm,

the float says 622 on it,

the main jet is a 120,

the needle jet is 106,

the pilot jet is 25,

the throttle slide is a 3 and has 622 stamped on,

and the needle is on the middle groove..

It was purchased from Sammy millers in the last couple of years.

Is this the jetting and set up for a 622 or 624 ?.

What would be the best set up for this carb on this bike ?.

any input would be gratefully received either posted on here or PM..

Thanks in advance.

H.. ;)

Edited by scoobie232
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Hi, All engines are slightly different & may require fine adjustments , but as a guide a B40 with an Amal Mk1 should run fine with a 624mm choke , 170 main jet , 3 1/2 slide & the needle in the middle notch ,.105 needle jet.Good Luck!P.S. The 622 was used on the C15 .

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