Topic: This weekend I'm picking up a 1980 CB125 for 100 bucks. Pretty excited

[grcamna2]

So I might need someone smarter than me here but I'm looking at this diagram and it's looking like the headlight's power does in fact get filtered through the rectifier and converted to DC. I'm seeing all output from the alternator going through the rectifier. Is that right? Also I wonder if it'd be a good idea to put a regulator rectifier combo unit on it? Is that an option since it doesn't have a regulator from factory?
 
Also a bunch of places online list it as Regulator/Rectifier even when searched with the Honda part number 31700-102-731. I'm bad with electrical systems to begin with so this is kinda rough for me trying to parse this info. Especially on a bike with very limited support online.
 
Oh also my headlight has a high/low switch. There's no off. I'm guessing that means it's not on a separate circuit?

Brent,I installed a 12vt. reg/rect. on my 81' CB125S w/ the 185 engine(same electrical system as the 81' CB125S)and that system uses a separate headlight coil And separate CDi coil built into the stator.
I would think one of the best ways to set-up your bike would be just like the early 74/75' CB125S where the stator gave all the power to the battery and then fed the complete system from the battery.The stator you have puts out AC and I would install a 12vt. Reg/Rect in place of your stock OEM 6vt rectifier.The other thing you would need would be to change everything over to 12vts.(lights,horn,coil,battery)and purchase a YB3L-B 12vt. battery which is the same physical size as your 6vt and fits perfectly in your battery box.I can take a pic of my battery box tomorrow where I mounted a standard '5-wire' 12vt. reg/rect.,a slight modification,piece welded to the front of the battery box(unless you get a good,used reg/rect from a Honda XL200R,XL500R,etc. which is a small size unit similar to your stock rectifier:I will text a picture of it with the number/description if needed)was what I did.

[WhyNot2]

So I might need someone smarter than me here but I'm looking at this diagram and it's looking like the headlight's power does in fact get filtered through the rectifier and converted to DC. I'm seeing all output from the alternator going through the rectifier. Is that right? Also I wonder if it'd be a good idea to put a regulator rectifier combo unit on it? Is that an option since it doesn't have a regulator from factory?
 
Also a bunch of places online list it as Regulator/Rectifier even when searched with the Honda part number 31700-102-731. I'm bad with electrical systems to begin with so this is kinda rough for me trying to parse this info. Especially on a bike with very limited support online.
 
Oh also my headlight has a high/low switch. There's no off. I'm guessing that means it's not on a separate circuit?

Brent,I installed a 12vt. reg/rect. on my 81' CB125S w/ the 185 engine(same electrical system as the 81' CB125S)and that system uses a separate headlight coil And separate CDi coil built into the stator.
I would think one of the best ways to set-up your bike would be just like the early 74/75' CB125S where the stator gave all the power to the battery and then fed the complete system from the battery.The stator you have puts out AC and I would install a 12vt. Reg/Rect in place of your stock OEM 6vt rectifier.The other thing you would need would be to change everything over to 12vts.(lights,horn,coil,battery)and purchase a YB3L-B 12vt. battery which is the same physical size as your 6vt and fits perfectly in your battery box.I can take a pic of my battery box tomorrow where I mounted a standard '5-wire' 12vt. reg/rect.,a slight modification,piece welded to the front of the battery box(unless you get a good,used reg/rect from a Honda XL200R,XL500R,etc. which is a small size unit similar to your stock rectifier:I will text a picture of it with the number/description if needed)was what I did.

I'd like to see this set up.

Will it work for a regular 6v CB100?

[grcamna2]

I'm not sure about hooking-up a standard 5-wire reg/rect,if there are as many stator wires.There may be a 6 vt. reg/rect. that can be used.
How many wires coming from your rectifier on the CB100 and what color WhyNot2 ?

[Pielz]

So I might need someone smarter than me here but I'm looking at this diagram and it's looking like the headlight's power does in fact get filtered through the rectifier and converted to DC. I'm seeing all output from the alternator going through the rectifier. Is that right? Also I wonder if it'd be a good idea to put a regulator rectifier combo unit on it? Is that an option since it doesn't have a regulator from factory?
 
Also a bunch of places online list it as Regulator/Rectifier even when searched with the Honda part number 31700-102-731. I'm bad with electrical systems to begin with so this is kinda rough for me trying to parse this info. Especially on a bike with very limited support online.
 
Oh also my headlight has a high/low switch. There's no off. I'm guessing that means it's not on a separate circuit?

Brent,I installed a 12vt. reg/rect. on my 81' CB125S w/ the 185 engine(same electrical system as the 81' CB125S)and that system uses a separate headlight coil And separate CDi coil built into the stator.
I would think one of the best ways to set-up your bike would be just like the early 74/75' CB125S where the stator gave all the power to the battery and then fed the complete system from the battery.The stator you have puts out AC and I would install a 12vt. Reg/Rect in place of your stock OEM 6vt rectifier.The other thing you would need would be to change everything over to 12vts.(lights,horn,coil,battery)and purchase a YB3L-B 12vt. battery which is the same physical size as your 6vt and fits perfectly in your battery box.I can take a pic of my battery box tomorrow where I mounted a standard '5-wire' 12vt. reg/rect.,a slight modification,piece welded to the front of the battery box(unless you get a good,used reg/rect from a Honda XL200R,XL500R,etc. which is a small size unit similar to your stock rectifier:I will text a picture of it with the number/description if needed)was what I did.

I'll probably do that at some point, thank you for the info

[Pielz]

Bike now has a functional tail and brake lights, headlight (it's wicked dim from being the wrong bulb), keyed ignition, Killswitch, and steering lock!

[grcamna2]

Which harness you running ?

[Pielz]

I've been fabricating what I need and using the one you sent me as a base!

[grcamna2]

I've been fabricating what I need and using the one you sent me as a base!

Have you considered my reply #100 here,setting everything up using the battery like they did on the CB100/125 ?

[Pielz]

Oh yeah turns out the headlight and everything runs off of the battery as is! It doesn't have to be running for the headlight to be on. So I didn't have to worry too much about it. I'm going to get a 6v compatible LED h4 bulb that is bright. The incandescent bulb that's in it does little more than nothing lol

[grcamna2]

That's the way that pt.#107(center code used for CB100 & CB125S early models with disc brake)wiring harness works.I would see if a 6vt LED will go right into that headlight,save you some power.
What rectifier you running ?

[Pielz]

This is what it looks like. I believe it's part number 31700-102-731
 
Next I just need the three bulbs that light up my dash panel for my high beam, neutral, and indicator light. I wonder if I could find one from another bike? There's a few on eBay they're just expensive.

[grcamna2]

That looks good.

[HondaMan]

When you rebuild the carb, SKIP THE KEYSTER KITS. Just get new rubber parts, like the bowl gasket and fuel hose. Keep the original brass jets, needle jet, jet needle, etc., because ALL of the aftermarket parts today for these carbs are Keyster, and dead wrong. The poor little bike will never run well with them, if at all. I'm fighting this front on both the singles and the CB500/550 bikes, big time. The 750 situation is similar, although more of their owners already know this about the Big Four.

[HondaMan]

I think this post is 'catchy', like the Kung Flu. I just tore down a (1972) CB125S for total rebuild tonight.

[grcamna2]

I think this post is 'catchy', like the Kung Flu. I just tore down a (1972) CB125S for total rebuild tonight.

 

[WhyNot2]

I think this post is 'catchy', like the Kung Flu. I just tore down a (1972) CB125S for total rebuild tonight.

Yep. I just picked up a CL100 a couple of weeks ago......