When the throttle is opened the accelerator pump moves down in the pump well and pushes fuel out through the main discharge.
To keep the fuel from getting siphoned off during power operation (not accelerator pump action), a check weight is used (G). This plugs the discharge hole until the pump is pushed down and the pressure moves the check weight (G) up and allows fuel to flow up through the discharge (J) and squirts fuel out of the 2 small orifices.
To test the accelerator pump:
Carburetor mounted – with engine off pump the throttle and watch the main discharge through the top of the carburetor. You should get a squirt out of the 2 small orifices (J).
Carburetor on bench – Top removed. Hold down the check weight while pushing down on the pump. You should get some pressure. If not then tap on the check weight (lightly) to seat the hole. With no pressure on the check weight and pushing down on the pump you will get fuel out of the discharge hole.
If gasket H is missing, or damaged fuel will leak into the float bowl instead of going out the discharge.