What Are Carburetor Floats

For an internal combustion engine to provide an aircraft with sufficient propulsion generation, both fuel and air need to be efficiently mixed and combusted throughout the duration of the flight. While there are multiple methods of producing and igniting fuel and air mixtures, many aircraft will utilize equipment known as carburetors. With a carburetor assembly, intake air can be measured and properly mixed with fuel to produce an optimal ratio for combustion. Typically, many carburetors will be a float-type, meaning that they utilize a carburetor float to measure and regulate fuel flow.

To efficiently measure and supply fuel, the carburetor relies on a number of essential subsystems, each working together to manage flow. Installed between the fuel supply and the carburetor’s main metering system is the float chamber, or “bowl”. The float chamber serves as a reservoir for carburetor fuel as it is supplied by the main fuel tank. As carburetors are incapable of conducting operations with pressurized fuel, the fluids within the float chamber are kept at atmospheric pressure.

With the carburetor and its main discharge nozzle, an almost consistent amount of fuel can be supplied to the carburetor for combustion. To prevent any risks associated with fuel leakage while the engine is not being operated, the fuel level within the float chamber is always kept about 1/8th of an inch below the main discharge nozzle’s hole. As maintaining the level of fuel within the float chamber is critical for a number of operational and safety reasons, a carburetor float and float needle are used.

As the carburetor float is meant to rest atop the fuel, it is often constructed from hollow plastic, metal, or a resistant foam. With its connection to the carburetor float needle, the float will move with the fuel as it is drawn from the bowl. As the carburetor float drops inside the chamber, it will open the float needle, causing more fuel to enter the chamber. Once a sufficient amount of fuel has been replenished to the float chamber, the carburetor float will rise enough to close off the float needle and stop fuel flow.

Although carburetor floats are simple in their design and functionality, it is critical that they operate correctly and do not cause issues in fuel flow. As an example, carburetor floats that corrode, crack, or generally lose buoyancy will not be able to stay afloat, thus causing the float needle to remain open. As fuel continuously pours into the chamber, it will enter the carburetor and flood the engine. As the float is adjustable, one should also always maintain optimal values of adjustment so that fuel mixtures are not either too rich or too lean. As a final issue to watch out for when using float-type carburetors, adjustments that are too low can sometimes cause stalls during high speeds. As the carburetor will pull an excess amount of fuel from the chamber, the fuel pump will not be able to keep up and fuel delivery will suffer.

Although float-type fuel carburetors have since been superseded by electronic alternatives, many vehicles and aircraft will still feature such types for their simplicity. At Limitless Aerospace, we are a leading online distributor of aircraft parts and components that have been sourced from top manufacturers we trust. Whether you are in need of screw throttle plate parts, arm throttle plate components, fuel pump accessory bearing cages, or other such aerospace items, we have you covered with our expansive inventory. Explore our various catalogs and listings at your leisure, and our team of industry experts are readily available 24/7x365 to assist you through the purchasing process as necessary. Start the part procurement process today when you submit a completed RFQ form as provided on our website


October 6, 2022

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