[Gaz64]

The "pump exhaust valve" is really a two way valve.
It allows fuel to enter the pump cylinder, hence "inlet valve" but as the pump operates, fuel will return to the float bowl until the inlet ball seats, hence "exhaust valve" even as a "00" valve.
A valve with a 0.35mm, 0.50 orifice on it's side bypasses fuel back to the bowl while the ball is seated.

A light spring with a closed "00" exhaust and 40 pump nozzles would give a long duration pump squirt.

A heavy spring with a "60" exhaust and 80 nozzles gives a short sharp squirt. Both extreme examples.

DCD, DCOE, IDF, and IDA all run this valve at the bottom of the float bowl.

The float on an IDA has to be removed to change the valve.

The valve is easier to change on the other carbs because the float comes out with the float lid, (airhorn).