Introduction: Make a DC Circuit for Your Honda CBF 125

The CBF 125 has a serious defect : An DC negative unsmoothed electrical system. So, kills bulbs with ease and prevents the use of xenon, LED's and other electronic components.

The solution? Turning things directly to the battery, but we must use a switch because otherwise things are always turned on. The solution is a relay.

The one i will be using has four contacts (pins), "30", "85", "86" and "87". The pins are connected as pairs, the "30" with "87" (where he have the switch) and "85" with "86", where there is the coil. When current passes in the coil the switch closes allowing current to pass. In other words, the aim was to find a "place" where the current pass only when we turn on the ignition (and remain with the engine running), and that obviously no longer provide power when turned off the bike. This "wire" goes to pin "86" (or "85", whatever) and "85" connects to ground (aka negative). Pins "87" and "30" (no matter the order) we will connect to the 12v from the battery and the other the electronics that we want to feed.
To summarize: When you turn the ignition key, current will pass trough the coil which pulls the switch and this allows the current coming from the battery to feed our gadgets.

The video below shows the result:

Sounds easy, but the problem is that all places where I would get the signal, the current was the AC, and the relay coil uses 12v, so the relay wil not work. Thus the relay does not help anything, but I did not quit, I ordered a relay and a 6v 5v to see if it worked, but also didn't work, the problem persisted. Solution (final)? A switch for xenon and no LED's.

However I got a month vacation and there I was back to see if it could resolve the matter. And I did. I was upset over the bike (ignition on but engine off) and started to press the brake, when my attention, a flashing light. It was the brake light. Now if this light was working with ignition on and the engine off, it could only be powered by the battery. I turned off the ignition and obviously the light no longer worked. I opened the bike, and found the plug on the brake pedal. There where 2 wires:

- Ignition off: 0v in both;
- Ignition switched on: 0v on one, 12v in the other, but under braking 12v on both;
- The motor is connected: a 0v, 14v another, but under braking on both 14v;

Note: with the engine running the voltage is 14v, not 12v because the battery is charging.

You found the ideal place to connect the relay coil! We will connect this pin to the wire that has 12/14v in the last two situations.

To make this modification you need beyond the usual tools (screwdrivers, pliers, etc. ...):

- Power Cord;
- Ties or connectors (or solder and soldering iron);
- insulating tape;
- 4-pin Relay with 12V coil;

Step 1: Open the Bike

Step 2: Wire to Use

You will find the wires in the photo. The black has 12v with ignition on and the green only has 12v when you press the brake pedal. The wire we'll use is the black, the green can be used for other mod's, but will only pass current when you press the brake pedal.

Step 3: Wiring the Relay

Then just make the connections in the relay. 87 to the black wire, 30 to the ground. 85 to the + terminal of the battery and 86 to the things you want to feed. Normally these relay can take up to 40A, but remember the diameter of the wire will limit the current.

Don't forget to use a diode n the relay, my socket has an integrated diode.

Step 4: Connect the Load

Now you choose what you want to feed. I took advantage and cut the wires of the quadrant, parking light (and later the tail light) to have LED's on these places. It is advisable to use a fuse in the wire from the battery (depending on load).

If you want to simply install an HID kit you can pick up the sleeve that takes the wires to the left handlebar, cut the yellow wire, isolate the side which comes under the deposit and connect the other end to the wire from the relay. (Ill make a photo later).

I hope I was helpful, and any questions just ask. This is was my first instructable, i'm my writing English is not that good.
If you want this guide in Portuguese you can see it on my web page: