AJS & Matchless Owners Club

Burlen Fuel Systems stock service items for Amal Carb.

Main jet 400, throttle slide 3, pilot jet 30, needle .106 at centre slot. I have recently bought a new 389 for my '59 Model 31 and due to it running too rich (today's crap fuel they call petrol!) have reduced the Pilot to 20 and increased to slide to 3.5 which I think now is too much, Surrey Cycles suggested trying dropping the needle to slot 2 instead.

Hello Laurence,
join the club to have full access at this forum, and to get all kinds of parts from AMOC Parts. For instance, AMAL carbs are cheaper from AMOC than elsewhere...
Kind regards.

I would also renew the petrol pipes. Ethanol in petrol can cause them to swell and restrict fuel flow. The club sell ethanol proof petrol pipe.

Jumping on this thread, which is reasonable as I have a 1960 model 31dl that is running lean, would a worn carb cause that? I checked all the jet sizes and needle position and they are all by the book. JA my club oracle has suggested a new carb will resolve the issue but if that's the case I'll need to hide my next credit card bill from the wife.

Mike

A worn carb will run lean more so at idle and just off idle as the larger clearance around the slide body will allow more air into the mixture. A new carb will certainly reduce the lean running low down but above 1/4 throttle you should find not noticeable difference. If it runs lean above that range it's needle and needle jet related but when they wear it usually causes rich running. I'd start by checking all the jets and airways are spotless especially the pilot jet and airway.