[squirrel_hunter]

Possibly the clutch switch?

Underneath the clutch leaver on the handle bar is a little switch that ensures you pull the clutch in before your start the bike. This switch or the connectors can become corroded preventing the engine from starting.

Disconnect the wires from the switch and bridge them with something suitable eg a split pin etc. and see if that helps. If the bike starts then its likely to be the switch, which is straight forward to test and replace if faulty.

Other that that it could be the starter switch... disconnect and test with a multimeter. These are the first places I would look.