When pushed down, the lever is supposed to flash the high beam, then spring back. Mine, as with several others I've tried, remained down.
Eventually, the horn stopped working altogether and the light became somewhat intermittent. Not good. At this point I decided to do something about the problem.
It turns out that, at least in my case, these switches aren't too hard to fix.
The almost identical (in appearance) starter/turn-signal switch on the right side was and still is fine so I didn't mess with it. All of the following information was gleaned from the repair of the left-hand switch. I suspect that it applies to the starter/turn-signal switch on the right side as well.
First you must partially remove the switches. There are two small screws that hold the switch guts into the pod that they live in. One is on the top, the other is on the bottom. Remove them.
This allows enough slack to pull the switch assembly out. Sadly, in my case it did not allow enough slack to really do much in the way of repairs.
This is no problem, just remove the pod. It is held in by a single screw in the center. Now you should be able to slide the pod down the wire towards the triple-clamp and have enough slack in the cable to allow work on the switch.
Now, you can get to the real meat of the switch. The button is held on by a spring 'C' clip in a groove on the switch shaft. When I worked as a TV technician, we called these clips "Jesus Clips". Why? This was the word most often used immediately after one shot across the room. Be careful.
To remove remove the 'C' clip, first you must be able to see, even fondle, it. It's buried in a countersunk hole in the back of the switch body. It's rather hard to see as it's shrouded by all the wires that are connected to the back of the switch wafer.
To get the clip out in the open where you can work on it, hold the switch body between two fingers and depress the button with your thumb. The shaft and the clip should now protrude so that you can reach it.
To remove the clip, insert a tool, such as a scribe or a tiny screwdriver, in the slots provided in the clip. Carefully pry against the shaft to remove the clip. It might be a good idea to practice your profanity before starting this step.
If you are really worried about the clip getting lost, you might want to put a dab of grease over it to contain it when it comes loose.
After the clip is off, you may pull the button off. Underneath it you will find a skeletonized triangular plate with bumps and a spring. The plate is the actual wiper of the switch, the spring presses its bumps against the fixed contacts.
Pay careful attention to the way the tabs in the plate engage the slots in the button. If you forget this, you can figure it out again (as I had to), but it's easier just to remember it. A hand drawn picture would not be out of place here.
At this point, you should have four parts, the button, the spring, the contact plate, and the 'C' clip free of the bike. The switch body and its pod should still be attached to the bike by the wires. They need not be removed for this job.
Clean the wiper plate with a fine wire (preferably brass-bristled) brush and some solvent. I used isopropyl (rubbing) alcohol. Don't attack any of these parts with an abrasive paper. You don't want to remove any more of the plating than normal wear already has.
Now clean the stationary contacts. Use a fine brush and solvent as well. My headlight contacts were almost black with corrosion. Don't forget the horn/starter contacts. They are above the contacts that the wiper rotates on. One is on either side of the bushing that the switch shaft rotates in. Mine were so black that I missed them at first. The color just blended in with the black plastic.
Now clean the contact ring that is located on the button itself. As you look into the business end of the button, you will find a metal ring buried deep inside. When you press the button, this ring connects the two contacts on the shaft bushing. Clean it in the same manner you have cleaned the other contact points.
No that all of the parts are clean, take some moderately stiff grease (I used wheel-bearing grease) and put a small amount on the switch shaft and the contacts. This will lubricate them and prevent corrosion.
Now reassemble the switch.
Take the button and insert the spring. Place the triangular plate atop the spring. Get it aligned the way it was when you pulled it apart. That drawing seems like a good idea now, no?
Insert the shaft back into the switch body.
Repeat the "Vulcan Nerve Pinch" procedure with your fingers and thumb, but this time instead of removing the 'C' clip, replace it. I find this to be the trickiest part of the procedure. I positioned the clip with a pair of hemostats, then pushed it into place with a tiny screwdriver.
Place the pod back onto the handlebar control assembly and re-attach it with its screw. Place the switch body back into the pod and attach it with the two screws.
Mechanically test the switch.
The turn signal switch should rotate freely and remain in the selected position.
The high/low beam switch should rotate freely and remain in the upper or middle positions. It should spring back from the lower (flash high beam) position.
Either button should depress smoothly and spring back.
Now electrically test the switch. With the ignition spike in (and the headlight switch on if you're working on the left assembly), try all the switch positions.
If they work, you are done. If they don't try again. On my first try I got the high/low beam switch working perfectly, but the horn didn't work. The second try fixed it. I hadn't done a good enough job of crud removal apparently.
I read your instructions on the thumb switch repair, and thought you'd be interested in a problem I had recently with my right-side switch.
It started smoking one day, and the right turn signals would glow faintly even when the switch was in the center position. Upon taking the switch apart, I found that the rubber supporting the contact ring was swollen and cracked. The ring was barely held on. It seems that the ring was being pushed up against its contacts, and lubricant was being burned at the contact point, which must have been getting pretty hot with the continuous contact.
I picked out the old rubber, and glued in a piece of Tygon tubing. I glued the ring onto the tubing. It seems to be holding OK.