If I turn my x540 off after mowing for a while it will not restart. It acts like the battery is dead. Nothing comes on when you turn the key. I have checked the battery, fuses, cleaned the safety switches and the ignition switch. If I leave it sit for an extended period of time it will restart and everything works as if it should.
When it is hot and won't crank, have you tried jumpering the starter solenoid? If it cranks, see if you have 12V to the coil of the solenoid when trying to crank. If not, you may have an issue with the Interlock Module (if the X540 has one).