The 1275cc Midget was fitted with twin SU HS2 carburettors of 1¼-inch bore throughout its production run. Three home-market variants were used, each identified by a number stamped on the aluminium tag attached to one of the float chamber lid screws. The tag will be suffixed ’R’ or ’F’ to denote rear or front carburettor.
Carburettor Needles
The AUD136 carburettor was fitted to 12CC engines. It is a non-ventilated design with no breather hose union on the body and uses a fixed (unsprung) needle. The AUD327 was fitted to 12CE, 12V586F, and 12V588F engines. It introduced a ventilated body with a breather union and also uses a fixed needle.
The AUD662 was fitted to 12V778F engines and is ventilated with a breather union but uses a biased (sprung) needle rather than a fixed one.
Needle Specification
The needle type is critical, fixed and biased needles are not interchangeable, and the correct needle profile must be matched to the carburettor specification. Service components including float and needle-and-seat assemblies, dashpot piston dampers, dashpot springs (blue for the HS2), throttle spindle kits, throttle disc kits, and gasket kits are available. The jets differ between front and rear carburettors. Complete rebuild kits containing the float, jets, needle, and full gasket kit are available, with the tag number required when ordering to ensure the correct specification.