Remove the small kill wire from the coil, and try to start. If you have spark then, either the kill wire is shorted to ground (not likely since you replaced it) ( insulation chewed or rubbed off and touching mower, or if equipped, On/Off switch is bad)
Are the flywheel magnets good? they should be strong enough to hold a large screwdriver and feel a good magnetic pull from 2 or 3 inches away, at least.
Also, how are you checking for spark?