In my experience it is very difficult to see the spark. If the ignition was checked out and validated you may have another problem as you well know.

Is the plug fowled?

Sounds like you may have replaced the pickup coil?

Is the cylinder obviously wet with fuel?

Have you verified the power is reaching the ignition module? I noted you deleted the switch, what about a bad wire connector or the like?

Have you cycled the battery with a load and verified the capacity? Even a battery which shows its "HOT" with a DVM may not be able to provide the required current to charge the ignition system.