Carburetor service and adjustment

The detailed procedure for the service of a carburettor is always specified by the manufacturers and varies in the case of different types. However, the general procedure and the points of caution are given below.

          To remove the carburettor from the engine, first of all, remove the air cleaner and disconnect the throttle and choke lineages. Next, disconnect the vacuum advance unit and any other connections that may be there. After that loosen the flange nuts and remove the carburetor gently.

Dismantle the carburettor and clean each and every component in the petrol. Detailed inspection of each part is then done and the faulty ones are replaced, after which the carburettor is reassembled and the flange bolts tightened. Remake the different connections in the order reverse to that done for removing.

The most important precaution is that the jets should never be cleaned with wires etc. rather they should first be cleaned with petrol and then with a blast of air. Secondly, you must work with clean hands, otherwise while assembling; the dirt from your hands will again go into the carburetor. Further, it must be remembered that any adjustments to the carburettor should only be done once it is first ascertained that the other components of the fuel system are working all right; otherwise, the engine performance will not improve.

However, the common adjustments and their procedure may be outlined as given below:

Idle adjustment

There is an idle adjustment screw provided in the carburettor. Screwing in the same decreases the idle port area and hence decreases the engine speed. The screw is adjusted till the engine runs smoothly at the required speed. Generally, this done by screwing-incompletely and then opening back by one or two turns. Another method for idle adjustment, which is precise, involves attaching a vacuum gauge to the inlet manifold and adjusting the idle screw till maximum vacuum is obtained on the gauge.

Throttle adjustment

On releasing the accelerator pedal throttle valve should be completely closed, while on pressing the pedal fully, it should be in full open position. This may be checked and if not found correct, the linkage may be adjusted, as provided for in the manufacturer’s manual.

Other adjustments

Apart from the idle a throttle adjustments, the other adjustments that are provided in some carburettors are for accelerating the pump, metering rod, floats etc. They may be performed as laid down in the manual.