Brown and Barlow carburetor

By 1910, the fixed jet carburetor was the most common type, giving a metered but averaged-out  quantity of fuel to the engine. The mixture was rarely correct for conditions. Then Clermont Brown of Brown and Barlow came up with the solution, a variable fuel metering jet. This carburetor had most of the features of a motorcycle carb we would recognize today. A tapered needle was attached to a slide that acted as the throttle in the main air tube, and slid through a tube as the slide was raised, metering out a precise amount of fuel to the air flow. There was an extra pilot jet for slow speed running while the throttle was closed or nearly so. B&B even included a tickler to depress the float to flood the engine for starting, a primitive solution that hung around into the seventies.

 The company had been in business for awhile and pioneered the idea of test rigs and even flow benches, which were constructed to draw air either smoothly or pulsating to test fuel mixing capabilities.  The modern carburetor had arrived.

D is the needle, F the jet tube.