Is SVS not a possible cause?
Highly unlikely with the bike being a 1600. It was a 1700 demon. Although it resulted from the valve guides not having enough clearance in the 05's(ish), it was also pretty much related to jetting,... IMHO
IMHO,....The 1700's were jetted to lean from the factory in the Pilot
circuit, which resulted in bumping into the Main
to much while at cruise(a sloppy transition), and caused the rich situations. Add in these bikes being cruisers, and many riders not wringing them out enough but doing to much putt-ing around(5th gear at 40), and the Carbon build up in the heads cropped up. If your asking for a wee bit more speed, and the Pilots to small you open the throttle a bit before the rpms
are up enough for good air flow through the venturi. The fuel slobbers into the throat around the needle, instead of whoosshing in with the rush of air needed for good atomization.
This is why people could go to a 40 Mikuni Pilot from the 35 stock, and a slimmer faster tapered needle(Barons or DJ
), yet drop the Main from a 182.5 Mikuni, down to a 172.5 Mikuni and improve their mileage, considerably. Often seeing gains from 5 to 10 mpg's, depending on their riding style. 95% of the time(a WAG), the SVS issues usually died with the rejetting.
The possible drive shaft failure is a real easy check. If that's good, then I think like Ctkog mentioned, I'd move on to verifying I didn't have a vacuum leak. I'd remove the intake manifold and surface the flange faces, and replace it using Hylomar or the Permatex Permashield(new orings, if the old ones look damaged). Just because it's a known issue. I'd double check the cap or plug on the AIS
port, on the intake manifold.
The OP is still concerned he may be fighting a short somewhere in the ignition circuit also. I'd make sure anything involved, was isolated from contact with anything from frame to throttle cables. I'd make sure they weren't touching anything other then what they are supposed to contact.