Nothing wrong with Mikuni Carbs their only equal are the original Amals before the bean counters took over and value engineered the monoblock and then the ultimate in cost cutting the consens*it
But one thing is for sure if the carb whatever it is is working OK don't change it!
Well 'Nothing wrong' really means they do their petrol control perfectly there are two small faults with Mikuni
one is the height at which the petrol enters the carb difficult on a Vincent tank the other is the retention of the rubber tube, never mind backfire blowing the carb off, I have done the clip up and watched it squeeze off ! (this is with a groove) the reason may have been oil on the tract but I simply used a piece of racing radiator hose that sorted it.
I could add a third fault but its more me than Mikuni I could never remember if the choke is up or down on that lever but I now know its counter intuitive