Use the second shut off valve.
The needle is supposed to stop the fuel from going into the cylinder then into the crankcase. Sometimes the needle doesn't seat properly. Sometimes the carb has a hairline crack in it but functions ok.
The fuel shut off solenoid is supposed to stop fuel from going into the carb when you turn the key off in order to prevent back firing from a hot engine.
Two telltale signs of gas in the cylinder are it smokes white when first starting and a vapor lock. You will need to change the oil and blow out the cylinder if this happens.