With your troubles, are you working on a 2 cycle, 4 cycle, single cylinder or maybe a V8????? Lets assume you are talking about a Chinese HT.
Rubber (although I wouldn't use it) will not cause NO spark, so long as the magneto to the CD wires are correct. It can make a difference in the kill switch depending if it's hooked up to the wires on the CDI/magneto connections, or to the bike.
Start.... Bad or wire not connected properly
Bad plug
Bad plug wire
Bad plug boot
Bad magneto/coil
Bad CDI
White wire mot used
Re solder the blue wire (cold solder joint)
How's them for starters??
If the engine is insulated from the frame, what good is the ground wire doing?