A carburetor’s main function is to mix air and fuel together in the correct ratio for combustion. The air/fuel mixture enters the engine through the intake valves and is compressed by the pistons. When the mixture reaches optimal compression, it is ignited by a spark plug, which causes the explosion that powers the engine.
The carburetor’s job is to make sure that there is always an ideal mix of air and fuel entering the engine so that it runs smoothly and efficiently. To do this, it uses a device called a vacuum secondary.
The vacuum secondary is essentially a small diaphragm located inside the carburetor that responds to changes in engine vacuum. As the engine sucks in air during operation, it creates a decrease in pressure (vacuum) inside the carburetor. This decrease in pressure is detected by the vacuum secondary, which then opens up a secondaries circuit within the carburetor that allows more fuel to flow into the airstream. This enrichment of fuel helps maintain optimal power and performance from your engine under various conditions.