When the throttle is opened rapidly, air flow through the carburetor changes almost instantaneously. Because the fuel tends to lag behind causing a momentary leanness, the accelerator pump system is used to provide the extra fuel necessary for a smooth operation.
When the pump plunger moves upward in the pump well, as happens through throttle closing, fuel from the float chamber enters the pump well through a vertical slot located near the top of the pump well. When the primary throttle valve is opened, the connecting linkage forces the pump plunger downard. The pump cup seats and fuel is forced through the pump discharge passage where it unseats the pump discharge check ball. It passes on through the passage to the pump jet where it sprays into the venturi are of the primary bore. The pump discharge check ball seats in the pump discharge passage during upward motion of the pump plunger so that air will not be drawn into the passage and prevent proper pump fill.
NOTE: The pump should not be changed from original factory setting unless gauging shows out of specification. The pump leve ris made from heavy duty, hardened steel making bending difficult. Do not remove pump lever for bending unless absolutely necessary.
