I have been having an issue with my 85 K100 not shutting off via key or kill switch. The only surefire method is pulling fuse 1.  I can stall it out, but would rather not use that as a fix.
I have checked the FI relay and it is good, the starter button is not stuck and the ignition switch is clean.
I did setup an acewell 2853, but I ensure everything was connected properly.
The bike runs perfectly without the key, I could probably go for a ride with the key out and it switched off...

I am not expert on the K wiring but it sounds like something that should be powered via the ignition and kill switch is getting a direct live feed from a permanently live circuit.

That was my thoughts as well, but I even tried a new wire harness and the issue persisted.  Could the ICU be at fault?

It won't have anything to do with the ICU or the FICU. They are concerned only with the timing of ignition and fuel. If the engine is running then these will be ok. This is a power issue.

It won't be a closed short in the Ignition switch because the kill switch would cut power to that anyway.

So it could be the kill switch itself has a closed short. Have you had it apart recently?

A more likely cause imo will be the Load Shedding Relay and or the Starter Relay.
Try swapping the LSR with the horn relay. They're the same.
Fried (open short) SR contacts will cause the starter to run continuously, requiring the battery to be disconnected to stop it. You can pull the cover off it to check out, clean the contacts and bench test etc.

Q: Do you have a starter button? Sometimes the button itself breaks and pops off.

I have not had the Kill switch apart, Ill swap the two relays and see the result as well as inspect the starter relay.

my starter button is good. i did check that. I will have an update after work