If your scooter runs smoothly at higher RPMs and idles almost OK, but is uneven and misfires at small throttle openings, Carb synchronization may be your problem. Carburetor synchronization is an important part of setting up the carbs. Apart from getting the pilot air screws and throttle stop screws correctly adjusted (using a vacuum gauges) it is most vital that all three slides start to lift at exactly the same time. A tiny difference at the bottom of the slide will translate to a poor tickover and irregular low-speed performance. Check those slides. Rather it be two, three or four carbs, the slides must lift simultaneously for smooth running. Stalling or chugging out of an intersection does not impress anyone. To remain safe and running smoothly check those slides!