Other carbs = big money to a wizard to make airbox and new manifolds , cables , then carb tuning etc to make hyosung engine happy to run it.
Mikuni being japanese is a good carb if the last owners did not piss them off, so i can understand your frustrations.
you have to explain in a lot of detail what it is doing ?
how does it start?
how does it idle?
is it worse when hot ?
what rpm is best for her ?
which rpms does it bog down bad?
have you replaced the pump ?
are fuel lines and vacuum lines kinked?
is the tap on the tank replaced or did you clean it ? (it has dirt trap at bottom too like a big square nut)
what size pilot jets?
what size mains?
go to mixture screws , replaced them? the rubber orings may have gone bad and is leaking out
did mixture screws got touched ? how many full turns out are they ?
as cobra says = float height is key