Carburetor doesn't like my overhaul ...

[amclass]

I have rebuilt my Zenith carburetor. Well, it's more a semi rebuilt/cleaning, since I didn't buy the complete kit with new jets. I cleaned all passages and checked the original jets. The float is parallel to the edge of the upper casing and the fuel level is 5/8" from the top edge. The engine runs at about 420 rpm, but it makes a "plock" sound every 2-3 seconds next to the usual "put put". I found that I can not only turn in the gas adjust needle completely, but also the air idle adjust valve and the engine continues to run at idle and only almost imperceptibly a little rougher. In addition, the carburetor leaks about 1 drop every 2-3 seconds after the engine is turned off. Here I suspect the float needle valve, that I have tested but will replace now with a new one just for the peace of mind. Before I disassemble the carburetor again I would like to know what could be causing these weird problems. Any ideas?

BTW: I rebuilt the engine as well since the car was stored for decades and I'm now braking in the engine. Therefore the engine only runs on idle since the rebuilt and I have no information how this carburetors is acting while driving.

PS: I used the instruction and advise of Tom Endy for cleaning the passages and to understanding the Zenith carburetor ... very informative and helpfull.