How Small Engine Carburetors Work

by Contributor

Small Engine Carburetors

Carburetors help to mix air and fuel for an internal combustion engine. Karl Benz invented the part, and later patented it in 1886. This component uses Bernoulli's principle--the faster air flows, the greater the decrease in static pressure, and the increase in dynamic pressure. Depending on the type of small engine, there usually can be one or more carburetors inside to meter the air flow entering the engine. A small engine carburetor also controls the correct air/gasoline mixture in the proper degrees. These carburetors contain circuits in order to function well under these conditions and execute different operating modes.

Basic Function

Air passes through the open pipe of the carburetor to the inlet manifold of the engine in the form of a venturi, where it narrows at a certain point then widens. The process causes the airflow to speed up at its narrowest part. Underneath, the butterfly or throttle valve works with a rotating disc that controls the airflow, and thus the air/gasoline mixture quantities the system will use for power and speed. The throttle connects via a cable or rods and joints to the accelerator of the equipment. The fuel mixes with the air stream through tiny holes or jets from the narrowest part of the venturi.

Problems and Prevention

As the fuel evaporates inside, a gummy substance forms that hurts the component's performance. Another potential problem is when the needle gets stuck and hampers the fuel flow within from mixing with the air that enters the carburetor. There are ways to fix these problems and prevent future issues. First, remove the gas from the carburetor by turning off the fuel line and run the engine until it dies, thus burning the fuel inside. Replace the air filter to help keep dirt and debris from entering the carburetor and affecting its performance.


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