CRC electrical spray contact cleaner works too. The Blue can is safe around Wing plastics
Whats the electrical path re: does the Kill switch disable starter on that model/year Wing?
Totally guessing on a gen I do not own, but as noted above- crud gets into switches and makes for weird problems.
What happens when you pull in the clutch, in Neutral? the ol worn clutch bushing syndrome is possible issue
While ck grounds may seem generic, on the Wing its a must. Plus relays being dirty, fried or loose wire etc.
Start with the cheap easy basic known problem areas, then proceed wildly if problem not fixed