Let me try my hand at this. I for sure don't know all there is to know about troubleshooting so someone correct me (please) if I'm wrong.
Kick starts fine so that leads me to the starting electrical system. Could be one of three things. The actual starter switch on the handle bar. An intermittent wiring short. The starter.
Probably need a wiring diagram for these.
You can visually inspect (for wear/cracks) the wiring and use a multimeter for continuity on each wire.
Manually make the connection on the start switch to make it start (can we even do this?). If it starts every time then it is the switch.
Not sure how to check the starter other than on my car when it doesn't start, I've tapped it with a hammer (don't over do it [at your own risk]) to get it off the "dead spot". If it starts then, I'd replace the starter.
How'd I do? Just trying to help. I've always been a little shy on giving troubleshooting advice because I don't want to say either some nonsense or just lead someone a stray.