Stupid quesition but have you even tested the battery? Does your headlight work if the ignition is set to on? Does the neutral and reverse lights work?
Trace the wires from the start button to the harness and connect a digital multimeter to them. Put the DMM in ohm mode. With the button out, you should have no continuity, with the button being pushed you should have low numbers on the DMM (showing continuity).
Start there. If you find the switch is broken, try jumpering the 2 wires together and see if that results in it starting. If it does, replace the switch.
If that doesnt resolve the issue or do what I said it should, report back. Ill try and help you as much as I can. My buddy has a Warrior I can check stuff out on if you need me to.