Sounds like one or both of the float valves is stuck or has debris keeping it from sealing off the incoming fuel. Sometimes you can just clean the float valve with spray carb cleaner and they will start to work again. You will need to remove the top off the carb so you can access these float valves. Also you must be careful to ckeck the float level settings as well. Not rocket science but take your time and be carefull. Good luck, Topless.