I've just gotten this letter from Burlen Fuel Systems and thought you would like to read it.
Dear Nortier,
All Amal carburetter bodies have part numbers which apply to the individual body and these are in the format 276/XXXX where prefix denotes the type of carburetter and the suffix is a number specific to the type of body and identifies the choke size and other features such as the handedness, method of attachment and any other specific features. Thus the M20 carburetter has a conventional 276/014 1" choke, right handed flanged body which can be found on a variety of bikes whereas the G3L carburetter body 275/402R is specific to the G3L as it has an unusual drain slot arrangement in the throat of the carburetter rather than the conventional spill hole above the Mixing Chamber Union Nut.
When these carburetter bodies were supplied as spare parts they were marked with the relevant part number e.g. 276/014R. However from the late 1930s on, whenever these carburetter bodies were supplied as part of a complete carburetter the flange was marked with an identification code which identifies the intended use of the carburetter, the specification and the type of float chamber fitted. A 276/014 body supplied as part of a carburetter to BSA for an M20 will be stamped 276C/1B and will be fitted with a 170cc Main Jet, .1065" Needle Jet, a 6/4 Throttle Valve and a bottom feed float chamber for a banjo connection. The carburetter body numbers are listed against the specification codes in the original Amal settings sheets. I've attached a copy.
I've also attached the Amal Service Bulletins which describe the changes to the carburetter identification codes and a couple of the Amal specification cards which list the carburetter details and changes.
There is no problem with using the old Amal tuning information. Let me know if you require any further information.
