PLease Help!!! I just bought a used 01 Sportsman 90 for my son on Christmas. It Won't Start....
It was running fine and then it just cut off and won't turn back on. We have checked the coil, kill start, cdi, changed the plug. Any other ideas?

 

I assume it's not getting any spark? Sounds like you have done a pretty good job at troubleshooting so far. The kill switch, ignition switch, and the kill switch rip cord are all high on the list of probability.