Which model was the ignition listed for? I looked up the 81 KZ1000 M CSR on Z1E and didn't see an ignition switch listed for it in the electrical parts section.
If the other 6 wires on the new switch work exactly the same as the 6 wires on your original ignition switch, then you can just connect the yellow/red wire on the harness to the brown wire on the harness, as long as the wiring is original, and the diode in the tail light circuit is working properly.
The reason you have the extra YEL/RED wire is to give an extra measure of safety in case you use the parking position on the ignition switch. The park position is designed to leave the tail light on while the rest of the bike is off. There is a diode in the tail light circuit, designed to prevent the tailight circuit from back-feeding power to the rest of the bike. However, if the diode was shorted out, power would go the rest of the bike. The YEL/RED wire was added to run ignition power seperately so that in case the diode shorted out, the ignition would not get power, even though the rest of the bike (lights etc.) would get powered. If you never use the park position, and/or as long as the diode is working properly, you can just splice the RED/YEL wire to the BRN wire at the ignition switch.
