The reason I was betting on stuck float was I have had both issues, no spark and no fuel. The intermitent nature would lead towards spark. But if the header was completely cold I would say no fuel to make the fire. Get a spare plug and hook the sparkplug wire to it on the bad side and crank the motor if theres spark then its prob fuel. Or crack the bowl drain on the bad side. This is easy and no gas=no gas every time.
