I have the same issue but I have replaced my voltage regulator and it still does it. I'm not sure if it's the stater/stator or what.

 

Is it charging 14-14.5 volts at the battery at an idle? If it is have the battery load tested. If it's not charging then it could be stator related. Plus do you know if you have the later model Kokusan or Ducati ignition? Under the front panel you'd have a separate cdi and coil if it's a Kokusan,a combo cd/coil module if you still have the Ducati ignition system that was junk.