Fuel circuit goes
Fuel filter > carb > purge > tank return.
Purge valves have a one way valve in them.
On carbs where the bulb is part of the carb it is replacable on remote ones they are not so new purge time.
Pull the tubes off the back and check the purge is working by putting you finger over one of the tubes.
Outlet blocked = can't press bulb in
inlet blocked = bulb will not come back out.
Double check that the carb is connected to the filter which is the thinner diameter tube with the heavier wall, because it is a suction line so prone to collapsing.
The return line is a bigger diameter and thin walled.
Nearly all novices hook them up wrong way round.