Norton Commando Workshop Manual

## Carburetor

# E

### SECTION E1

### DESCRIPTION

The Amal concentric float carburetor proportions and atomises the correct amount of fuel, mixing it with the air drawn in through the air intake. The jet sizes, choke bore, throttle needle, and throttle slide cut away ensure that the correct fuel/air mixture is maintained at all throttle openings. Initial opening of the throttle brings into operation the mixture supply from the pilot jet system which controls the idling speed.

As the throttle is progressively opened the mixture supply is augmented from the main jet which discharges through the needle jet into the primary air chamber and goes from there as a rich fuel/air mixture through the primary air choke into the main choke. The earlier stages of the throttle opening are controlled by the throttle cut away and the taper needle which passes through the needle jet, the taper allowing more fuel to pass through the needle jet as the throttle is opened.
The Amal concentric carburetor is of the type 930 of 30 mm cross bore size on the Commando and type 932 of 32 mm cross bore size on the Combat high performance engine. A carburetor is shown in exploded form with part descriptions in Fig. E1. A common airbox serves both carburetors, this being covered in detail in Section E10.

### SECTION E2

### CARBURETOR REMOVAL

For ease of handling it is recommended that the carburetors are removed attached to the spacers as a pair as follows:
1 | Disconnect the fuel lines from both fuel taps.
2 | Remove four socket screws and washers securing the spacers to the head - a shortened socket key is needed for ease of access.
3 | With the balance pipe and cables still connected, lift the carburetors and manifolds away from the cylinder head, disengaging the flexible air hoses at the same time. To service the carburetors individually:
4 | Disconnect the balance pipe at one end.
5 | Remove the two cross head screws and washers securing the carburetor top.
6 | Lift off the carburetor top, throttle and air slides with cables attached. The top and slides can be left hanging from the cables but the exposed parts should be protected from damage by wrapping in clean cloth.
7 | If required, remove the second carburetor in similar fashion, removing the fuel line by taking off the banjo bolts.

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