Does anyone know what an Amal "pump" carburettor is? I've seen this term used in catalogues describing the special equipment on Blue Star models, but as far as I'm aware the carburettor is just a standard Amal 89. Am I missing something, was there an accelerator pump fitted in the main jet like on square bodied Dellorto carbs?
David
I think the parts are like the first photo and the part numbers as the second photo.
From 1935 Amal parts list.
Thanks once again Julian. Just as I thought, this uses the same design as the Dellorto carbs - or rather Dellorto used the Amal idea!
Shame my Blue Star has lost the original carb.
David
David,
The pump part was offered as a kit by Amal to be fitted on standard 75, 75, 76 and 89 carburetor. The pump itself only chokes the engine but the bottom part of the pump can be found on jumbles, it is the float bowl which is the most difficult part as it has a bigger hole to accommodate the bottom nut covering the pump. The pump is an elongated needle jet with a spring loaded 4 hole piston in it. It is pushed down by the needle and if you open the throttle quickly it will spray some additional fuel through the needle jet in the mixing chamber. At least that is the theory.
Regards,
Leon
Thanks Leon. My machine has a Martin Bratby reconditioned 289 fitted. Do you think the accelerator pump made much difference to performance? Not that I'm really concerned about gunning an 84 year old motorcycle around the Suffolk lanes! However, I would like it to run nicely. The crank's away for expensive reconditioning work and the engine has never been run with the recon carb.
David