Where is the fuel leaking from? Going by the info provided, so far, I'd expect that it's coming from the overflow tube. That would mean that the inlet needle/seat assembly isn't controlling the fuel flow to the carb. Fuel keeps flowing in until the level rises above the overflow tube, probably even higher than that...then the engine floods.
Too early to say that the carb "needs" a complete rebuild. First step is figuring out the cause of the leak. I'd pull the carb & remove the float bowl, then the float. Shake the float, if you hear liquid inside, it's leaking and should be replaced. If not, check the level and inspect the needle/seat; there should be a spring-loaded plunger inside the needle...I've seen them missing, a result of a POs effort to "fix" a malfunctioning carb. Note the appearance of the float bowl, it should be clean; if not, a carb rebuild is more than just a good idea. If the engine runs well, with the carb as-is, then it's worth rebuilding. A new replacement needle & seat asm is part of a rebuild kit.
