1983 Maxim 750 motor dies

I have a 1983 Yamaha Maxim XJ750, 11,000 miles, always garaged. Starting last year it started to stall on me. It would start up cold with no problem. After running 5 to 10 minutes the motor would go dead. Everything else would sill work. A few times when this happened as I was going down the street I tried turning the ignition on and off, also the kill switch  -- nothing, not even a pop. It would go from running perfect to dead. When I roll to a stop, it won't start, the starter cranks but no ignition. Within 15 to 60 seconds it will start up and run perfect the rest of the day --  even on a 200 mile ride. If I take it out two days later, it will do the same thing. It always does it once a ride, it has never done it twice.

It seems to me to be an ignition problem the way it goes from running great to dead and back instantly. I would think something breaks a conection at a certain temperature.

Is anyone aware of this issue, tracing intermittent electrical problems is such a headache.

Thanks,
Al