The needle valve is not seating on the rubber seat in the carb.  Did you just clean it or did you install a repair kit when you had it apart.  If you installed the kit maybe the rubber seat isn't sitting square and not sealing, or a piece of dirt is stuck to the seat.  Also check your float height to make sure it is within spec.  Also make sure the float doesn't have a hole and sinking if it is the brass float.