Does the heat riser work? Not sure. It moves freely and with a cold engine the counterweight is in the down position. Its probably not a good idea to put a torch on the spring with all that extra gas hanging around. It will be a few days before I can start it to see if the heat riser works. Would that cause flooding?
Yes it would. If the heat riser was stuck in the open position, excess exhaust heat at the base of the carb will cause the fuel in the bowl to boil and the resultant pressure forces fuel out past the metering rod jet. There’s your flooding after shutdown.
Heat riser works. Put a propane torch on it and counterweight goes up, cools down and counterweight comes back down. So that rules that out. I want you to hold the lollipop between two fingers then lift rapidly until you here a clang. Then let it drop for the second clang which verifies there is a valve plate in there.
I’m pretty confident that float is set right. I won’t doubt you there.
What else could it be? Should I unscrew the needle seat to make sure it is installed right and no burrs are present? Not necessary.
Is it possible there is a crack somewhere in the body which causes it to leak fuel? I don’t think you have a cracked bowl.
Could one of the passage end screws be leaking? Any of the caps or the lower aluminum plugs could be leaking. All caps should be tight. All plugs should be driven in tight, but not totally squashed. The most likely culprit is the big cap with the screen in it. Use extreme caution however when tightening these. Soft metal is easily destroyed if not handled carefully.