Looking in the parts book/wiring diagrams, it seems that the 125 Hummers has an extra coil and set of points for the brake lamp system.
My engine on the 1957 125 Hummer does not have that extra coil and set of points.
When I did the restoration on this machine I had bought the brake lamp system but never installed it.
Yesterday, Monday, I set about doing just that.
My over thinking mind would not rest, The over thinking portion was about how much voltage the extra filament of the brake light would draw and possibly destroying some component of that charging system in the process.
I got online and did some searching, found a supplier that has 6 volt LED bulbs that are AC voltage compatible. The ordering instructions said that if the tail lamp has an old thick lens cover to order the white colored bulb. If it is a newer thin red lens then to order the red colored bulb. I ordered one of each.
I then came off of the tail lamp wire at the front lower of the rear fender screw/grommet/nut with a wire and made it long enough to reach the brake lamp switch, another wire from the brake lamp switch to the screw/grommet/nut that has the brake lamp wire back to the tail light attached to it.
These LED bulbs are not an easy install.
They have a flange just above the base of the bulb that does not allow them to seat into the slots, then make that slight turn to seat them into the grooves that the bulbs pegs fits into.
Removed the tail lamp, a piece of pipe that fir over the back side of the bulb socket.
On the inside of the tail lamp housing, after removing the license plate lens, used a punch and a hammer and punched down the portion of the socket that is crimped agains the tail lamp housing. making it flatter until I figured that the bulb would be able to make its slight twist/turn and be seated into the fixture.
Wrong, the socket had flattened enough but it also squashed inwards in two positions, firht above the bulb seating grooves of the socket.
A dremel tool and a small die grinder burr and removed a slight amount of metal from those two areas.
Now the bulb can slide into its grooves and give that slight twist to seat it into its socket.
Assembled the tail lamp back onto the machine and plugged in the tail lamp wires, fired up the engine and that LED buld works just fine.
It does have a bit of a flicker at idle but it is very bright with the engine revved slightly, and, the brake lamp works too.
Now I am happy that just one more item is functionable after putting this bike together so many years ago.