Horn: There’s a turquoise wire that connects to ground in the handlebar switch when you push the horn button. The connector the switch assembly connects into does not have a mating wire. So, it looks like two options: 1) Simple way is you can run a positive wire off the grey wire to the horn positive and connect the turquoise to the ground lead on the horn. Or, 2) More complicated, but better IMHA. First cut the green wire going to the horn switch 3/4” from the solder joint. Then jumper that to the grey on the turn signals (all inside the switch housing, new connection is the black line in the photo.) Now the turquoise wire will be positive when you push the button. You can then hook the horn negative to any ground and the horn positive to the turquoise. Edit: Looks like option 1 would mimic a KTM EXC and possibly more consistent on the GPX models and option 2 would be the way most Japanese bikes are wired.