Have not seen your carb but most have a smaller needle that rides inside the larger one. The float arm pushes on the smaler needle and in return the smaller needle pushes the larger one closed. In the carbs I have worked on the larger needle had no adjustment. The tips of these needles could be worn, very hard sometimes to see with the naked eye. Have you completely cleaned the carb?? have you tried a new spark plug?? What's the history with the bike?? Example: 1)Ran good last week but not today. 2) Bike sat for two years without being used. 3) Just bought the bike and never heard it run.