Bare bones electrical

I am trying to get a cb125s2 running but don't want to mess with the lights,accessories. So here is a brief synopsis of system.

There are 4 leads coming from the alternator. Green/red going to neutral, pink,white, and yellow. White connects to a yellow/white and runs to the headlight control. Yellow runs to headlight control and connects to the yellow/white when the headlight is switched on to provide more juice to charge the battery when the headlight bulb is on. This all then goes to a frame grounded rectifier. Pink goes directly to rectifier. Red/white comes from rectifier to charge the battery and a fused red is pigtailed from this to the ignition switch. The battery is frame grounded. A black (switched hot) then runs from the ignition switch and runs to power the system when it is switched on. The black runs to power various systems but of concern is the headlight and kill switch. The kill switch connects the black with a black/white to the coils.

My question is this. I want to run with no lights, switches (getting replaced) or accessories just to get her going and then add new control switches etc. I am wondering if I need to tie the white and yellow from the alternator together and then bypass headlight control connecting directly to the rectifier, or will this over charge the battery since there is no regulator? The rest of the system will remain unchanged except that when starting the bike I will by pass the kill switch (or purchase a simple one from radio shack) and connect the black/white to black.

I know this is long but it needs the detail. I have some concern about overloading the battery so any knowledge will be appreciated. Thanks in advance.

I have attached the wiring diagram which may help.

I downloaded the schematic and these are my feelings:

It's interesting there is no regulator. Coming from both vehicle wiring and guitar amp/effect pedal experience, a voltage regulator is always needed with an alternator unless a stable source is utilized (wall wart or battery). If I remember correctly, alternators generate varying amounts of voltage and current depending on how fast they spin. Higher RPM=higher output. Alternators also put out AC current, which has to be rectified (by the rectifier) to convert it into a primitive form of DC. In electronics capacitors are used to smooth the ripples in rectified AC current, but in non-computer controlled vehicles "lumpy" DC current is acceptable since its just lighting up filaments and jumping spark gaps.

Enough boring theory. If I'm reading this schematic correctly, it looks like the switch shorts the Y and Y/W connections in the "off" position. This makes it appear that it's the opposite of what you thought. Headlight "off" effectively disables a section of windings in the alternator, reducing voltage. Headlight "on" opens the Y + Y/W circuit, adding juice from the alternator. If I have it correct, then you can simply leave the wires disconnected with no bulb. In fact you can just leave the connector unplugged from the switch leads.

Lucas,

Everything you mentioned is pretty much correct. If it were me, I'd add a new regulator/rectifier (we sell them for $35, free shipping) then just run the white and yellow spliced together and direct to the R/R.

If you don't want to buy the R/R or run with the lights on, you can ignore the white wire and run the yellow and pink directly to the existing rectifier.

You'll notice that the battery is a large one for your bike. Something in the 9Ah range or so. The reason for this is that the old battery acts a lot like a regulator. The excess voltage is consumed by the battery and generates heat which boils the electrolyte. It's one of the reasons why sealed batteries don't work on these very old models. Upgrading to a new R/R will let you run a smaller battery and swap from flooded cell to something more modern, too.

Sonreir,
Do you have a voltage regulator that would work with the 6v system? I'm in Portland so if your close I could pick it up. I have a sealed battery and read the output voltage at mid range rpm and it runs at 8v so I need to get it regulated before I ignite myself.

I have a slightly used one that's still good. $20?

Sonreir said:

I have a slightly used one that's still good. $20?

Click to expand...

Is that the one from me? If so, it never had power go to it. Just mounted, but never run.

deviant said:

Is that the one from me? If so, it never had power go to it. Just mounted, but never run.

Click to expand...

Yup. That was one yours.

That works for me. Looks like your aways south in Albany. I think mail would be the best way to go. How should I go about getting you the cash?

PayPal to sales@sparckmoto.com and I'll get it into the mail.

Thanks again.

Money has been sent. I really appreciate the help. Cheers.

I received the regulator in the mail yesterday, thanks for sending that so quick. I am going to try and install it today but did notice a black wire. I have a 6v so run the 4 wire rectifier. Can I leave the black disconnected presuming the red lead still charges the battery via converted AC, the yellow and pink come from the stator and green goes to ground?

Nope. Black wire is the voltage sensing wire and will need to see power when the bike is turned on.