Typically, these carburetor leaks are initially noted as a drip from the lowest part, the drain plug, and the typical response was to put a wrench to the plug and tighten it up. Since this often had no effect on the leak, the owner then wrenched it even tighter causing a hairline crack in the threaded portion of the casting.
On several occasions I have tried everything to solve a carb leak before discovering the real cause to be that hairline crack in the casting, which is usually impossible to see when the area is soaked with fuel.