OK, now we're making some progress. Do you have an inline fuel filter between the pump and the carburetor? A real filter- - -not one of those clear plastic things. It's beginning to sound like you're getting some sort of sediment into the needle valve assembly which is allowing the carb to flood periodically. Also shake the float to see if it's got some gasoline in it. Brass floats are soldered together, and they're notorious for springing leaks. A float partially filled with gas can't develop enough upward pressure to keep the needle valve closed properly when the float chamber fills. There has to be some reason for the flooding, which is obviously what's happening. You're having to rev the engine up enough to burn the extra gas and prevent the mixture from getting so rich the engine won't run. I'll also make a guess that the exhaust pipe(s) are black and sooty, and the spark plugs are black, as well. Find and fix the flooding problem, and you should be back in good shape.
What sort of "sealer" did the radiator shop use? It could be flaking off and contaminating the fuel.
Jerry
