Identifying your Carburettor

Minis produced in Australia have been fitted with three different types of SU carburettors: single 1.25", twin 1.25" and single 1.5". This is a quick guide to identify what carburettor your Mini has to help source the correct parts for your car.

1.25" HS2 Carburettor

Minis were originally fitted with a single 1.25" SU carburettor, referred to as the HS2. The HS2 reflects the size and type of carburettor, the number indicating the number of 1/8s over an inch the carburettor is (HS2 = 2/8s over an inch = 1 1/4"). All standard Minis from 1961 to approximately 1975 were fitted with a single HS2 carburettor.

The main identifying features of the HS2 (compared with the later HS4) are the float bowl and the top damper chamber. The float bowl on the HS2 carburettor is mounted to the passenger's side of the carburettor (on the later HS4, it points towards the drivers side). The top damper chamber is attached with two screws diagonally opposite (where it is mounted with three screws on the later HS4).

Mini Coopers and Clubman GTs were fitted with twin HS2 carburettors. For the purpose of rebuilding, these carburettors can be treated the same as the single HS2.

This is the early HS2 carburettor. Note the float bowl points towards the passenger's side of the car.

1.5" HS4 Carburettor

Later model Minis and Mokes from 1975 on were fitted with the larger 1.5" HS4 SU carburettor (HS4 = 4/8s over an inch = 1 1/2"). Mini Matic models were also fitted with this carburettor. Identifying features of this carburettor are that the float bowl points to the driver's side of the car, and the top dashpot chamber is attached with three screws, rather than two on the earlier carburettor.

Later model HS4 carburettor. Note the float bowl points to the driver's side.

'Doughnut' style filter fitted to HS4 equipped cars as standard.