What goes where? Electrical wiring issue…

Hey everyone,
I finished my 1980 XJ 650 4kO and am waiting for my license plate (complete off chassis rebuild, engine rebuild ‘till the last nu & bolt).
It runs great but one thing I couldn’t figure out are two unconnected wires on the bike.
1:

yellow and black wire, under the tank and goes into the main cable line to… ?

2:

Black (ground?) wire, next to the diode.
Only thing not working on the bike is neutral light. Pretty sure neutral switch is ok and wires didn’t get pinched. So… pretty sure it has something to do with the neutral light connection, but can’t figure out what goes where… already tried to ground the black wire, no result…

help!

 

Yellow and black is for the rev limiter I think. It goes to the instrument panel. Neutral switch wire is blue. I have a black wire which is not connected to anything like the one circled. If all else is working it should be ok to leave it. If you don't have a Haynes manual you should get one, wiring diagrams are in that.