I did test the bulb and it's fine (continuity between the lug the green wire connects with and the black wire connects with).

I don't even have voltage at that green wire so it's something else. I'm testing voltage between green wire and ground (when running and main switch in position 2 of course).

Yamaha wiring colors can be a little confusing, especially if a US model.

The hi-lo switch circuit is very simple.  And since you have high beam, that means you have AC power coming out of the key switch to the handlebar switch.  

In the headlight bucket, the solid blue (could be blue/white) feeds AC power into the hi-lo switch.  When the handlebar switch is set to low beam, the blue wire connects to the solid green coming out of the headlight switch.  When hi beam is selected, the blue wire in now feeds the yellow wire out.  

Here's a screen grab from your video showing the part of the handlebar switch that matters for your problem.  The blue wire in the center is the "AC power in".  The solid yellow and solid green are on either side of the blue.  When you slide the beam selector switch, you are connecting the blue wire in to either the yellow or blue out. 



So either the contacts are not good in that section of the switch, or you have a bad wire green wire or green wire connection.

One thing to keep in mind is there is very little "load" when checking continuity with a meter.  ( A good example of this is sometimes a car will play the radio when you turn the key on, but then when you try to start, a bad connection in or at the battery fails under the extra load and everything shuts off) Those solder joints in your switch don't look too good.  

 

Another quick test is that, if I remember correctly, the headlight connector plug has 3 bullet connectors to the harness?  Simply swap the green and yellow bullets at that plug.  

If the headlight works now with switch in low but not high, you have a bad headlight or headlight plug.  

If the headlight still only works with switch set to high, headlight is good but there is a problem with the green wire getting power from the blue wire with the switch set to low.  

"One thing to keep in mind is there is very little "load" when checking continuity with a meter."

Good point. I'm trying to learn more about electronics and this is a good reminder.

"Those solder joints in your switch don't look too good."

Agreed. I actually had to resolder the blue wire yesterday because it came loose as I was taking the switch apart again.

I'm really leaning toward bad contact in the switch between blue and green. I'm going to jump it there to see if it's a contact issue. Of course I have this pesky thing called work that I have to do today  

Make sure that the copper strips (plate?) in the internal switch are making good contact with the copper contacts on the fixed, sort of semi circular part.   

Make sure that the copper strips (plate?) in the internal switch are making good contact with the copper contacts on the fixed, sort of semi circular part.

This was/is the issue. I disassembled the switch again and re-soldered the wires. While doing that I noticed there is some side-to-side play in the switch.

Both beams are working now but if I put a little lateral pressure on the switch it does break contact. It's good enough for me, I just want both beams working in case I need it for some reason.