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A brief History of the Binks Carburettor called the “Mousetrap”

In the early days of 1910 not much attention had been paid to special carburettors for racing


The late Mr Charles Binks, designer of the first four cylinder motorcycle, had been directing his

attention and inventive genius to making motorcycles flexible, and he was evolving a carburettor

with 2 jets – the principle of which turned out a success.

In this 2 jet carburettor the pilot jet made the engine run slowly, so it was possible to experiment

with the main jet for speed alone as it’s alteration had no effect under 15 mph. This main jet was

surrounded by a variable choke tube which was useful for tuning up and flexibility, but when closed

it was of a shape that did not lend itself to speed.

The next step was to produce a carburettor with an efficient air passage, the “venturi” shape being

adopted. This was found to be wonderfully fast, but there was always the feeling that if the throttle

could be opened wider the engine would go faster. Larger choke tubes around the jet were tried

with amazing results of speed, but it was difficult to get going, and consequently the acceleration

was not what it had been.

Then came the inspiration – a variable “venturi” tube to give speed, and acceleration with no

throttle to impede the flow of gas.

This early carburettor won hill climbs, carrying all before it and quickly found its way to Brooklands,

being used by Mr. O’Donovan, Mr. Graham Walker and others. We called it the “Brooklands Model”,

until some ingenious fellow saw the similarity between it and that domestic article the “Mousetrap”,

by which name it is now known all the world over.

Within a year, no hill climb was complete without the sensational starting up and easy get away

given by this instrument, and its success was assured. It is going as strong as ever today but

improved and adapted to fast road work and various conditions.

The Binks “Mousetrap” Principle

The success of the “Mousetrap” Carburettor is unchallenged, and you may ask why does this

instrument give such teriffic accelleration. The answer is that whilst the engine revolutions are

mounting, the cylinder is getting a full charge of gas – gas which is the result of the fuel being well

atomised by a violent draught of air crossing the jet and breaking up the liquid into the finest


The beautiful shape of the “venturi” tube allows the gas to slide into the cylinder with the least

possible skin friction, even though the narrowest portion around the jet may be restricted to create

the necessary suction.

The air flow across the jet does not in itself draw the petrol from the jet. The force with which the

fuel leaves the jet is caused by the atmosphere in the float chamber pressing the liquid out of the

nozzle into a space which is filled with air at less than the the pressure of the atmosphere. The force

of the air blast drives the liquid into a spray, as may be seen by looking into the “Mousetrap” with

the engine running.

The closing of the air shutter is analagous to the closing of the air plunger of the ordinary type of

carburettor, but in the former case the air flow is speeded up and does not simply increase the

suction on the jet. Hence, the bigger volume of air as well as of petrol.

For sheer speed the “Mousetrap” is ideal, as the gas has a better chance of filling the cylinder since

the shape of the tube offers the least possible resistance. When the engine speeds get high the

difficulty is to fill the cylinder with gas, and the power curve falls.

The “Mousetrap” keeps the supply up to a higher range of speed and efficiency.

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