Replacing the entire wiring harness to cure a rear indicator problem is overkill. It may be something as simple as a dirty or corroded bulb holder.
It would be helpful to identify exactly what the problem is and exactly which motorcycle you have. There are some significant differences between the various KZ models.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough