Let fuel sit in a carb bowl for five days -- very hard start

Gas is not your problem. It's an issue with the small rubber(?) o-ring that sits
under float-bowl valve. Gas with ethanol will harden the o-ring over time and fuel will leak around the o-ring and flood you engine.

I've had this problem on motorcycles and weed-wackers - replace the o-ring with one made out of Vitron (?) and problem solved. Draining the float bowl temporarily solves the problem.