I have a 1968 ct90 that looks great, mechanically sounds but after new piston and rings I can’t get it to start. Chain timing correct. (Not 180 off), spark advance assembled and installed correctly(not 180 off), compression stroke identified by exhaust valve position, points timing set statically. Points gap set, spark plug gap set, great spark, but absolutely no pop! Compression 100, tried starter fluid, no pop. Replaced spark plug/ no pop. Tried wiggling spark plug to see if positional- still good spark. Air filter connected but not exhaust. Argh! Next option new engine. Any ideas??