I'll agree with otherwise that the static timing should be very close, so either it's way off, your pipes were already blue from age, or that Mikuni is set really lean.
One other thing to consider: 3 phase stators and their voltage regulators call for resistor caps on your spark side. (at least the sparx units do) Apparently they are sensitive to the plug wires and from what I have seen first hand, it can wreak havoc on your charging side, boiling batteries and such.
from sparx:
**Single & Three phase boxes***
Due to the sensitive nature of both the single and three phase boxes it is VERY important to fit spark plug caps of the 5000ohm resisted type.
Failure to do so will cause overloading.