Amal Concentric question

I have a pair of Amal 932 carb body's that do not have the pressed in pilot jets.
However,they do have the possibility to fit the threaded pilot jets on the underside of the carb body's
My question is: what size of screwed-in pilot jets should be used, and will there be any noticeable difference in running compared to the pressed-in pilot jets.

Peter R said:

I have a pair of Amal 932 carb body's that do not have the pressed in pilot jets.
However,they do have the possibility to fit the threaded pilot jets on the underside of the carb body's
My question is: what size of screwed-in pilot jets should be used, and will there be any noticeable difference in running compared to the pressed-in pilot jets.

Click to expand...

#25 pilot. Probably no differance in running, just less crap from the pressed in system. As a rule, I drill out the pressed in jets from the back side, drill and tap 10-32 and cut off a couple extra throttle stop screws and add a fresh oring.

Amal switched from the screw in jet to the bush after the first year of Concentric production. Four stroke engines ran poorly on the first Concentrics and the location of the pilot jet was one of the changes introduced to improve running. The screw in jet is too far from the pick up point in the throat of the carburetter for the majority of four stroke engines and causes symptoms such as irregular idling, poor pick up and cutting out on the overrun. However the severity of these symptoms depends on the engine, those with a stronger manifold vacuum being less effected. Large capacity or tuned engines such as Commandos may well work with the alternate location of jet .

It is noticeable that now Amal are offering a four stroke carb with a removeable jet they have re-designed the carburetter to ensure the jet is in the same location as the bush.

Thanks for your replies, I will have to buy a pair of #25 pilot jets, and see how it will turn out.

I would add a set of Stay Up Floats to the order. Float height adjustment may be critical and these make life so much easier.

I am using a single Amal 1038 Concentric carburetor on my 850. It was originally made for a 2 stroke so it has the pilot jet at the joint face for the float bowl. It works perfectly. The idle is very steady.

All the other parts have been changed to 4 stroke items.