First, gravity will flow fuel to the carb, if the fuel tank outlet is above the level of the carb. Second, the carb float / needle & seat should stop the fuel in the carb bowl when in gets full (if working correctly and / or don't have a piece of trash in the seat letting fuel bye) no matter if it's gravity or pumped (with a pulse pump.....an Electric pump with a carb, is a different story). Third, take a GOOD close-up pic of this carb, with this "overflow line from the float" and post it!
Tried to upload pick and attach a file of carb but kept getting message file to big so no go with pick. I did take the open end of overflow rubber gas line and tried to blow through it and nothing but put suction on it and got flow and could hear gas being sloshed around in carb bowl, don't know if that is signification or not. Got it to crank and turned off gas supply valve and it ran pretty smooth for a bit and didn't cut of and would run until gas in carb is gone. I am leaning toward fuel pump, again very cheap so will prob replace and see what happens. Thank you guys for help, I,ll report back.