Welcome to BHQ !! If you don't have a Clymers repair manual , get one. Check ALL grounds are clean, bare metal, especially coil. I think coil has to be ohmed with boots off. Ohm boots seperatly also. Trim 1/4 in off plug wire before putting boots back on= new clean wire.
On my son's I had to pull flywheel, clean poles on stator , inside of wheel, and lugs on out side of wheel to get rid of a mis-fire. Set pick-up gap at .018. JMHO, your results may, and will vary.