There is another carb you can use that is sold here that isn't a "smog" carb with fixed orifices. I wish I found the part number but if you have the numbers off the side of your engine OldMiniBikes warehouse will look up the carb for you. It has a slow jet and main jet external adjustment which is invaluable! No more changing jets to get peak performance. It's a direct bolt on which lines up with the original throttle linkages or whatever you currently have now.
I think I paid $35 for the carb. Beware of that primer bulb leaking, that may be your culprit.