I have seen JUST the carb for 40 bux.
they seem to do Ok I have not tried one..
I would assume they allow the engine to turn a lil harder, may sacrifice bottom end on a stock engine.
with an intake adapter, filter, and carb 100 bux..
Mikuni corp makes ALOT of different carburetors ranging from stock EPA carburetors on lawnmowers all the way to 58+ mm slide carbs. The most common sized Mikuni used on a stock GX200 with a stock sized intake valve is typically 22 mm. It is a roundslide carb and works pretty well on these motors.