Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Hello how are you today? When you turn the fuel off and run the fuel out of the carb the float valve that controls the flow of fuel into the carbs bowl opens up, some times corrosion builds up, this corrosion will stop the valve from closing and the issues you are having appear. At this point, the carb will have to come apart and the valve cleaned, or replaced, depending on the condition.
I would also suggest the oil be changed, spark plug replaced, along with the air filter.