Recheck the timing, recheck your carburetor settings, especially float height - I don't think they're correct.
One coil fires #1&4, the other #2&3 cylinders - which cylinders are struggling ?
The spark plug caps have internal resistors that you can check with an ohmmeter.
Also check the high...
It looks like (from the parts list) that the switch is held on to the upper triple clamp by two 4X12 flathead screws. Maybe no drilling required ?
Replacement switch part # 60011066000
I owned one.
Crappy fuel mileage because of the small tank (90 miles ?) and an overly complicated cam chain tensioner system.
I sold mine for parts when the cam chain sawed its way through the back of the cylinders.