HOW DOES A PUMPER CARB WORK?
Carburetors with accelerator pumps are euphemistically called “pumper carbs.” The accelerator pump gets its fuel from a special gas reservoir hidden inside the three-bolt cover plate off to the right side of the Keihin FCR float bowl. Here is how a pumper carb works: (1) A rubber diaphragm covers the accelerator pump reservoir. When the throttle cables rotate the carb pulley, they activate the accelerator pump’s link lever. (2) A rod at the end of the link pushes against the center rivet of the accelerator pump’s diaphragm. (3) When the diaphragm is depressed, it creates pressure (much like squeezing a balloon). This pressure squeezes gas out of the accelerator pump reservoir. (4) The fuel blasts out of the accelerator pump nozzle into the throat of the carburetor. Underneath the nozzle is a one-way check valve that prevents air from entering the circuit when the accelerator pump isn’t squirting. In essence, turning the throttle turns a link, which compresses the diaphragm, which squir
