Your wiring harness points to the hard-wired switch: the B/R wire connects to it, and the G/R clutch sw lead on these bikes is now a straight shot from the solenoid and is no longer associated directly with the start switch, so that's why there's a spare B/R lead and no G/R at this end of the wiring harness.
So, with the correct switch installed, the right hand switch leads are B/W & Black from the kill sw, B/R & Y/R & Black from the start/headlight button. The Br/W lead for the headlight dimmer connects with the left hand control, which should have a HI/LO switch.
It sounds as if your hard-wired switch has self-destructed at some time in the past (surprise, surprise) and the PO installed an earlier model control on the right side. Did the starter work before? Did you have headlights? If so, the PO probably made some modifications to the harness.
This might be helpful:
Here are some ways to get around this problem proferred by two of the forum's heftiest authorities. When you find your switch is no longer functioning, Hondaman suggests the folowing:
"There are 2 easy solutions:
1. Inside the headlight, find the wire that feeds the middle fuse of the fuseblock. This circuit usually has a Blk/Red or Blk/Brn wire coming from that Start button, and it may even change color to become Blk/Brn enroute to the fuse, right there in the headlight. For example, the wire from the switch might be Blk/Red, but is plugged into a Blk/Brn to go to the fuse. Honda had some of these foibles in the 750"F" bikes...at any rate, you can unplug the feed wire to the fuse from teh pushbutton, then plug it into an available Black circuit in the headlight. This will leave the headlight always ON when the bike is ON, but it works.
2. If you want to still keep the "off when starting" function, you can install (or buy one of my kits for a prebuilt version) a relay that follows the Start button and disconnects the headlight from this same Black wire circuit. It's simple to do: just feed the relay's COMMON terminal from the Black circuit and connect the middle fuse's wire (usually Blk/Brn on 750 after 1974) to the NC contact on the relay. Then ground one side of the relay coil to a Green wire and connect the coil's (+) contact to the Start solenoid circuit (usually Yel/Red in the 750). Then this relay engages when the Starter does, opening the power to the fuse for the headlight.
The keyswitch on these bikes controls the taillight circuit, not the headlight circuit."
And Two Tired adds:
"There are a few alternatives for repair.
1 - replace the entire control group. It seems the newer replacements use a different plastic material than earlier ones, which seem to be more robust.
2a - Replace the switch with a single pole button for the starter.
2b - Then hard wire the head light on with Key switch control. (This lowers voltage for coils during electric start.)
3- same as 2a but add a switch elsewhere to control the headlight power.
4 - same as 2a except add a relay for the headlight that disables the headlight when the starter solenoid is energized."
