It's your choke. I guess a 4 stoke will have an auto enricher mounted on the top carb?. If so, it's activated by the engine starting, it's directly fed from the stator. When the engine starts, 12 volts will be applied to a heater in the enrichener, as it warms up a piston will extend cutting off the excess fuel needed for starting. It will stay cutting of that excess fuel until the engine stops. To test the heater check the ohms should be 15-25 @ 68 F To check operation, remove from engine, visually inspect the needle for damage, measure how far the piston protrudes from the body, apply 12 volts and wait a few minutes. Measure again, Is piston protruding further? Yes , it's working, No, it's broken and needs to be replaced. Remove the volts, let it cool and the piston should slowly retract to starting position.
