In hopes of saving someone else a ton of time and a headache I figured I'd put up a recent problem and solution I ran into on an Agility 50 that came into the shop.
Bike would turn over but wouldn't fire when it was brought in. Working off the principle of needing spark, gas and air I started by pulling the plug to check it out, looked good, cleaned it up and put it back in. Put a test plug in to check for spark, nothing using the kick starter. Was about to start testing the coil wire but on a whim I decided to try it using the starter switch. I turned on the ignition and the plug was arcing without even touching the starter switch. Did a quick check in the manuals I downloaded a while back and couldn't find where this problem was addressed. Also checked this forum. I figured I had a bad ground somewhere and tore off all the body and front panels.
Long story short the CDI was bad. Plugged in a new one and the bike fired right up. Got some carb issues but that isn't related to the original problem.
Hope this helps someone.