I would like to pass on a trick I was told about today that I tried and it works very well indeed. My Honda NC50 Express carb would not turn off fuel when the bowl was full. No amount of cleaning helped. The needle valve could not stop the flow off fuel. I was told to try a Q-Tip with a mild abrasive compound in a slow drill motor. I tried this using a small dab of Valve Grinding compound. You could use Chrome Polish, Toothpaste or Bar Keepers Friend as a mild abrasive. I 'polished" the valve seat for two seconds.You cannot use too much pressure as the Q-Tip stem will bend and break. In that short period of time the valve seat was shiny and perfect. I washed out the seat with Brake Cleaner. I filled a small gas tank with distilled water and raised it five feet above the carb via a gas line. The bowl filled and shut off perfectly. Problem solved. If you need to clean/re-seat your carb float needle vale,give this a try it really works. It may save you $$$.