Jump battery + terminal to starter motor power terminal with heavy cable. If starter motor activates, your problem is in starting circuit; if starter motor does not activate, you have an internal problem with the starter motor itself.
A wiring diagram and multi-meter are your friends in cases like this one. Clymer service manuals have the starting circuit isolated; otherwise, you can Google, "KLR650 Wiring Diagram" and pick your way through.
Starting circuit problems might be in the starting circuit relay, or the safety switch logic, or in broken connections, etc.