heh, heh.. ignition is fully electronic. Ignitor uses bumps on flywheel to set off spark. Trigger wire at each coil should show signal like this. High full-time with occasional drops to ground to dump coil and fire sparks. Won't show up with test-light because pulses are too short. Solenoid lights have duration-extending circuitry so bulb stays lit long enough for human eyes to see. It always seem to be the left channel that goes out for some reason. Maybe sharing signal with tach may have something to do with it.
Definitely not fuel-related as carbs don't gum up suddenly, then clear themselves while you sit on side of road.