Have you tried a new or different spark plug ???

I bought a new E3 spark plug for it. But I guess I could always buy another one and try it.

A friends YB100 Had this problem, gap the point correctly and checked timing,, , then she fired ,

A couple more things I am sure you tried, but it won't hurt for me to throw out there. When you turn the key to "on" position, does the neutral light come on or do brake lights work indicating the ignition switch is functioning?

On my 74 my neutral light would not work. Long story short, the wire was broken on the inside of the wire covering. It took me using a multimeter on each wire in the harness to diagnose this. Perhaps a wire in the harness is broken.

Is your coil cap making contact with the coil wire? Remove coil cap and verify. I am gonna guess it's that new coil or you are grounding out somewhere, but electric is not my strong suit.

you and i have the same bike.
ground your battery.
iground your engine with a wire.
ground everywhere.
i purchsed an aftermarket coil and it did not work. i went back to my original coil. sand frame for good ground. your points magneto connection plastic block take each wire out and wire brush the tiny contacts. over time debris oxidation and flim blocks contacts both ends within connection block. i had to re crimp on some mine. . air our your stator and sand between points gently. you gotta go thru your connections and clean em out thei the bike. mostly ground.
thats a start. oh and put a 12 volt halogen headlight instead of 6 volt. it works great and dont burn out at all!
gary in fort worth texas