Start at the plug and work backwards..
Coil, grounds, switches, stator, connectors..everything is a suspect. How did you 'check' the kill switch..did you see if it's shorting with a OHM meter or just see if it clicks?
It manual and meter time! Lots of specific testing 411 in the book..
We can't give you a specific since all we know is what you know.
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)