Re: voltage on blk/yel (kill wire)
If I may clarify that posters statement 'voltage on the Yellow/black kill wire'
With the motor OFF, and the ignition switch turned ON, there should be NO VOLTAGE on the Yellow w/black wire.
If the motor is cranking OR running, then voltage may be present from the ignition module, grounding this kills the ignition to kill the motor.
It can be easy to test with a common Volt/Ohms Meter.
DISCONNECT the Yellow w/black wire from the ignition module on the motor, then test Ohms to Ground with the ignition switch OFF, you should have GOOD continuity.
Switch your meter to volts, turn the ignition switch ON and test for Voltage, you should have NONE, if ANY VOLTAGE, disconnect the yellow w/black wire from the ignition switch and retest, If now you have NO VOLTAGE then replace the ignition switch.
Battery voltage supplied to the Yellow w/ black kill wire WILL DESTROY an ignition module.