Well, I think I got. It took me a long time, but i'm pretty sure this is correct. I was missing a spring and that was throwing me off so I made a new one out of a spring in a pen. Those are perfect size replacements.
Since there wasn't a write up for the left controls I took the time to do this, hopefully people find it helpful. It will not be as detailed as Sohon's but hopefully it will give you the visual that you need.
This is the Rebuild for a 1977 left control with hi/low beam, horn, and L/R signal switch:
My controls started out very faded so I painted them when I was painting the rest of the bike. I used the same SEM Hot Rod Black.
Little parts everywhere so be sure to work in a place that you won't lose them. I worked over a box with foam in the bottom.
First I put the Hi/Low switch back together since you can do this outside the control enclosure. This gives you better room to work on it. It took me about 4 tries but I think I got the right orientation since all the other ways seemed like something just didn't fit quite right.
Then Pin goes through the board side into the switch lever.
using the bracket that has an L shape to it and two holes on one side, this will go on the other side of the switch and secure the switch to the control enclosure. Notice the ball bearing slides between hole one or hole two. On the switch it goes Ball - Spring - Copper plate. The copper plate is on the opposite side of this photo and contacts the paths on the PC board of the other side as you move from Hi to Low beam.
Next I assembled the slider switch for the L/R signals. I didn't take much apart on this in the cleaning sequence, and it's pretty easy to get this piece back together like this. I did however lose that spring that goes behind the ball bearing. I pulled a spring out of a regular pen and it fit great with some trimming. It actually added a lot of tension to the switch and there's a much better feel to the switch now. Getting the ball to stay in was probably the most tricky part of the assembly.
Put the ball in the hole and push the spring down. Then push the ball against the back wall of the enclosure to hold the ball in place. Slide the control down until the ball falls into the V grove and push the rest of the assembly to the bottom. It will take a few tries but over all not really that bad. It helps to hold the control enclosure up in the air above the assembly to get started.
Secure the slider switch with it's bracket. you can also install the piece of the switch that rotates it back and forth and give it some test runs. There was two washers I had from the disassembly. I assumed they went here, because there was a gap without them. I'm not hundred percent sure on their orientation but the switch operates as expected so I left it and moved on.
Add the bracket to hold the cable back.
Back to the bottom part of the enclosure, install the horn switch. There is a cone spring that goes in between the button and the plate. It's pretty easy to figure out, but I don't really understand how the horn actually works. The button doesn't seem to connect anything to complete a circuit, it just touches the pad. When bolting down the horn switch this one will have the longer different screw from all the other brackets.
For the Hi/Low switch you put the bracket you see here on top of the L shape bracket from a few pictures up. This secures the switch to the enclosure.
After that there is one more cable secure bracket that is a larger plate, shown on the second photo. I secured it in the only orientation that it would fit on the last available hole, on the same side as the hi/low switch. Sorry I forgot to take a picture but it's pretty intuitive how it goes.
I hope this is helpful, as this forum is so helpful to me.
