A few possibilities:
Fuel tank vent plugged. Fuel line too close to heat source. Fuel line deteriorated internally. Engine cooling fins need cleaning. Charging system not working up to full voltage, which will affect the fuel shutoff solenoid in the carb. Dirty air filter. Dirty fuel filter. Key switch, all battery power except the starting circuit comes from the key switch also engine shutdown. Control module. Corrosion in plug in connectors. Carbon buildup in combustion chambers getting hot and causing detonation, to list a few!!!!
Mad Mackie in CT:biggrin::laughing: