Engine Repair
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Tips for Cleaning a Carburetor

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"Tips for Cleaning a Carburetor"
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Image by: John Ledbury.

Why a carburetor would need to be cleaned. ( As an aside, it is spelt: carburetter, in Great Britain ) In a Europe still recovering from almost six years of war, and a case of make do and mend, it was quite usual to have to clean a carburetor.

Often petrol/gas would be contaminated, mainly with water condensation or sediment, that had entered the fuel storage tanks through a variety of reasons. Unlike today, back then in Great Britain during wartime, motor fuel was rationed, and was always in short supply. There was just one brand of fuel available during Wartime, it was called 'Pool' petrol. Supplies would come in to the Country from wherever it was available, by the various petrol Companies, and put into the 'Pool' system.

Very few British cars, vans, or trucks that were powered by petrol, had fuel filters, which meant sediment etc ended up sticking the carburettor float, or blocking the jets. Driving an ordinary small saloon flat out at 45mph, which was good for those days, usually ended with a bang and a splutter, and a gradual coasting to a stop at the side of the road, was usually diagnosed as a dirty carburetor.

Cleaning a carburetor became a regular maintenance job. In the those old days, the most common makes of carburetors in use in Britain were AC, Solex, SU, and Zenith. Generally, Ford used Solex, Austin used Zenith, Morris used SU, and Vauxhall used AC, though there were variations of that. Although each brand was of a particular design and different from the others, the cleaning methods were very much the same.

To do a thorough job of cleaning a carburetor, and replacing any worn jets or a damaged float, the best way is to remove the carburetor from the engine and place it on a cleanand dirtand dust free work bench. Use of an airline to blow through the jets and passage ways is a great benefit.

Before dismantling the accelerator cable or rods and the choke/strangler cable, make a mental or written note of how they are secured to the carburetor levers. Carefully remove the return springs if fitted. With the carburetor free of cables etc, remove it from the manifold, it is usually held by two studs, but some use three or more.

Take special care when lifting the carburetor from the manifold, after removing securing stud nuts: between the carburetor and the inlet manifold there is a fibre block, used to give a secure and airtight seal. These can stick, and any excess pressure can damage the carburetor flanges.

The float chamber is usually secured with two large screws: unscrewing them releases the float chamber, but take care as the float is held in place so as to pivot, by means of a needle valve. This valve opens and closes, according to how much fuel is needed by the engine.

The jets are screwed into the centre tube of the carburetor, which is also called the Venturi. There could be three, four, or even more of what looks like jets in there. These are usually known as the starting jet, slow running jet, idling jet and main jet. Make a note of which jet goes where, before removing.

With the carburetor now stripped of all of its components, cleaning can commence. First wash all of the parts carefully with petrol/gas, ensuring that any specs of grit etc are washed away. If you have use of an airline, hold the jets tightly and direct the air into the jets orifice. ( Never directly blow compressed air directly against your skin, or fool around with an airline, compressed air can be as lethal as a gun.)

When all parts have been washed clean, and there is no trace of sediment in the float chamber, re-assembly can start. Drying the components can be done with a clean dry lint free cotton type cloth. Where applicable, fit new gaskets, these are the paper type washers that go between two metal faces.

When the carburetor has been re-assembled, re-check all screws, nuts and studs, for tightness: making sure not to overtighten any of them. The correct torque for tightening nuts etc, can be obtained from the Car Manufacturers Workshop Manual, but generally tight means tight, without undue pressure.

Refit to engine and reconnect accelorator and choke/strangler cables or rods as fitted. Finally recheck the carburetor to engine joint for air tightness. Obviously, any airleaks here will dilute the mixture of air and fuel going into the engine, and will greatly effect performance. Take vehicle for a short run to test, and recheck all joints and screws etc in a week or so for tightness.

More about this author: John Ledbury

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