1981 CB125S Wiring Help Needed

Black Dog Moto

New Member
New to site and new to this old Honda. I'm having a few issues that I need help on. First and foremost, I'm having a heck of a time finding a proper wiring schematic for this bike. RoyalRider's thread a few posts down is correct from what I can tell, but I need a higher quality image. His thread also answered a few of my questions.

I'm good with the mechanics, but some of this electrical is giving my very small brain some fits. Issues below:

1) The keyswitch assembly is all sorts of mangled up, and with this build I want to eliminate it anyways. I can use a screwdriver to change the switch position but it's very much not handy. I have no need for a "park" option. I have the keyswitch assy from an XR50 I want to use. It's the same function as the right side handlebar on/off switch. With the OEM switch assembly disconnected, I don't have light functions. How (what wires to connect/remove) can I modify the wiring so that this xr50 switch will both be in run and have lights when the bike runs? I am not using the idiot lights as that's all busted up as well, so those circuits can be eliminated. I'm fairly certain I can fumble my way through this if I could get a quality schematic.

2) When I got the bike, the lights appeared to be working normally. The battery was not connected, but I had decent headlight and tail light emission. The previous owner gave me a "new" 6v battery, so I filled the electrolyte and attached the battery. I took the bike out and rode around town for about an hour. By the time I got home, the lights were dead. Battery was dead. I tested the stator and found one phase to be out, so I sent the stator to Rick's and got it repaired. Installed stator and ran temporarily without battery. Headlight is very dim, tail light does not illuminate. Tail light does work, as the headlight dims when brakes are applied, but you can't see it. I charged the battery and installed, lights work. I didn't get a chance to run it to check if battery is being charged. I'm not terribly confident that the issue is fixed with the new stator, but this may stem from my lack of knowledge on the subject.

I'm wanting to ride the bike for a month or so until winter gets here, then the bike will get a 12v conversion, led lights and complete cafe treatment. The wiring fits I'm having is really pointing me towards the motogadget mo.unit. The price doesn't turn me off, but I don't believe I absolutely need it if I can just better understand the OEM wiring and remove the OEM keyswitch and idiot light circuits.

Any help is much appreciated.
 
At idle, with battery hooked up I’m seeing 5.81 volts with headlight on low. I don’t have a tach, but revving to a higher level I can’t get it above 5.89v. Is this sufficient or should I be looking for issues?

Edit, I think I have more issues that what I realize. I’m only measuring 7v coming from the stator and there’s a weird rattle from inside the engine. This may accelerate my complete tear down so I can worry about the wiring later.
 
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Most of these bikes will output less voltage than needed at idle, so that is fairly normal. You want to measure at 3-4k. Jon Pardue makes a nice R/R upgrade for the 6 volt systems.

“Weird rattle” could be any number of things. On any “new to me” bike I always go through the tuneup procedure, setting the valve clearance, points gap and timing, carburetor cleaning and adjustment.


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