'78 CB125T 6v to 12v

jjc839

New Member
Hi all,

Just finishing up the restoration of this bike, but I'm concerned the reg/rec is shot. This bike has the 3 phase alternator, so 3 yellow, a red a black and a green coming from the RR.

I tested the resistance between the red and the 3 yellows, zero. Changed the polarity and again, zero. Repeated the process between the green and the 3 yellows, but again, all zero's.

I've had the bike running but unfortunately not long enough to test the charging system and now I've got the carbs apart for a re-kit.

My question is, since the 6 wire 6v RR seems impossible to find, would it be best to change to 12v? I can get a plug in 12v RR for dirt cheap, and the availability of lights and batteries would obviously be much better. Can I use the stock coils?

Any advice much appreciated.

Sent from my SM-J200Y using DO THE TON mobile app
 
First up, your bike isn't a three phase. It's a single phase that someone has added a three phase R/R to it.

I don't know of any 6v systems that use three phase, so I suspect someone has already tried the conversion to 12V.

At this point, I would worry about getting the bike running before you mess with the charging system too much.

When you get to that point, let me know. We carry a few different electrical components that might make your life easier.
 
Sonreir said:
First up, your bike isn't a three phase. It's a single phase that someone has added a three phase R/R to it.

I don't know of any 6v systems that use three phase, so I suspect someone has already tried the conversion to 12V.

From the manual, is this not a 3 phase alternator?

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Sent from my SM-J200Y using DO THE TON mobile app
 
I'd give a 12V unit a try and see how it goes.

All of your components will need to be bumped up to 12V versions, though. Lights, coils, battery, etc.
 
Sonreir said:
I'd give a 12V unit a try and see how it goes.

All of your components will need to be bumped up to 12V versions, though. Lights, coils, battery, etc.
In case anyone is doing 6 to 12v, the bike is now finished and running great.

I purchased a generic 5 wire regulator/rectifier off eBay for $20, and spliced it in where the old 6v R/R went.

I didn't want to buy new 12v coils, so i wired in a 2 ohm, 50w resistor to the ignition wire (black on this bike) that energizes the coils pre-start. When the key is switched to ignition I have 6.2v going into the coils.

Changed all bulbs to 12v except for the front indicators, and kept the stock 6v flasher. With the combination of front indicators being 6v, rear indicators 12v and a 6v flasher, it works great, don't ask me how.

I couldn't find a 12v battery to fit the 6v box, so I bought 4 A123 LiFePo4 cells and soldered them in series to give 13.2V.

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Starts, runs, charges, turned out great.

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