I would check the wiring to the coil.
you might have a marginal ignition switch wire connection, bad connections at a resistor ( if installed ).
hot wire the coil, and try to start.
If no better.. check spark.. is your coil old? or a 6v coil and a resistor? if yes to either.. get a napa ic 14SB.. run new wires and new ignition switch just to start fresh. and don't run headlamps thru the ignition switch.