I always have to ask this because everyone's meaning of "won't start" is different. Does it fire at all? Does it backfire thru carb? Or is there absolutely no firing, no trying to start? You did say no spark at 3 plugs, so I assume no fire at all. Now that you have replaced everything, you might as well do the coil. It's all cheap. Hopefully you did not buy wrong or faulty parts. That is hard to catch because you think it's something else. If it will not start after coil, Double check all parts. Points, rotor, cap and correct internal/external resistor coil and of course GROUND WIRES AND HOT WIRES and coil to dizzy wire, for breakage or chafing.
Don't know what you have but have to mention ignition switch not sending hot to coil or foot start side terminal not sending hot or bypass resistor problem. You may want to jump from batt + to coil + and try.
Hopefully the new coil will do it.
After going back and reading, I want to be sure you know how to set points. Points have a phenolic "follower" that rides on dizzy shaft lobes. Follower must be on top of a lobe, then loosen screw just enough to allow points to rotate and open/close to achieve proper gap, then tighten screw. (You can bump starter or turn crank by hand to get follower on cam lobe) There is enough gear backlash to rotate shaft back and forth to check the operation of points because gap may change when tightening the screw. If you know all that, disregard, not meant to disrespect your knowledge.
