Question on Mercarb 2 barrel

[supercab78]

I have rebuilt a Mercarb 2 barrel on a 1984 140 hp IO. This carb is the one with small accell pump. The reason for the rebuild was the accel pump wasn't working properly. It would not put out a good stream until kind of far into the throttle, about half way. After the rebuild it is some better. When giving it slow throttle from an IDLE it still puts out a dribble in the beginning instead of a good stream. I did replace the T bar, spring and check ball under the venturi cluster, put the correct screw in the center of cluster plus check ball under accell pump. I have done at least 100 carbs through the years but after several attempts this is about to stump me. My question is are these 2 barrel known to have a weak accell. pump just off idle?