Start by acttually testing the ignition components with a VOM, as per the instructions in your manual. Sound like bad SP wires at the least. Next verify that the carbs are set to the correct INITIAL adjustments. More adjusting may be required after warm-up. Is the Gas fresh? Is the battery Strong, having 12 volts is only a partial answer.
93 VT1100C Harley Killer (1150cc), VH Exhaust, 2mm sleeved and bored, Modified Heads and Valves, Adjustable Timing, Touring Seat, Baby Apes, Metzlers