Yes that’s were battery negative is landed. Pull it and clean..,
I’m interpreting the “kill switch “ as the off/run switch on the Rh control. I don’t think he has addressed the ignition switch... I’ve heard of lots of problems with voltage caused within the ignition.
Magilla covered the ignition switch when he checked the fuse followed by the kill switch. He had no drop between those 2 points.
If he had 12 volts at the fuse then 9 volts at the kill switch, then yes...the ignition switch could be the issue.
You did look at it.
You have to see where the switch sits on the schematic.
It sits between the fuse and the kill switch.
Your problem is most likely between the fuse and the battery or on the ground side.
One other fact that might play a part in all of this is that while I had the tank and carbs off (intake ports were plugged) we had a 5" rain over the period of a few hours and everything was drenched. The bike is living on my patio right now so was not covered.