That's a doosey! Does the coil lead fit properly on the coil? I'm guessing you changed the parts with all new ones. I wonder if the carbon button in the dizzy is touching the rotor properly?

You can isolate the ignition switch by hot wiring it just to test. That'll at least rule that out. Just run a lightish cable from the battery to coil +ve (light so it'll burn out if something is wrong).

I'd be suspecting the cap or coil lead or the connections to them.