Headlight Replacment for Cb125e




Hi Guys,

This instructable will be on how to replace the headlight of a Honda 2012 cb125e motorbike with a luxeon star 7 LED light. The oem headlight for this particular bike leaves much to be desired as it only has a 35/35W halogen globe. The reason that i took on this project was because:

1. I wanted to have a headlight whereby I could clearly see were I was going (it uses a 1645 lumen light).

2. Have a light that consumed very little energy (consumes 15W on high beam).

3. Was relatively cheap to build (AUD $90 for the LED, LED driver and the 20 deg lens, the other electronic parts was under 3 bucks)

4. I love to tinker :-) 

The features of the project are:

Brightness on the low beam is easily adjusted via a 5k pot.

Intense low beam allowing you to be better seen during the day.

Uses only 15w on high beam.

Uses original head light assembly.

Parts List

Luxeon Star 7 LED - http://www.luxeonstar.com/Cool-White-5650K-7-LED-Round-CoolBase-Assembly-p/sr-02-wc310.htm

700mA LED driver - http://www.luxeonstar.com/700mA-Externally-Dimmable-FlexBlock-Driver-p/a011-d-v-700.htm

Khatod 20 deg lens - http://www.luxeonstar.com/Khatod-20-40mm-Medium-Beam-7-LED-Optic-p/pl121125.htm

25v 220uF electrolytic capacitor - http://www.jaycar.com.au/productView.asp?ID=RE6324

1N5404 diode - http://www.jaycar.com.au/productView.asp?ID=ZR1014

Copper Sheet - Got mine from eBay

Tools and materials needed

Soldering Iron
Heat shrink
Electrical tape
1 x 1m red heavy duty hook up wire (18 AWG)
1 x 1m black heavy duty hook up wire (18 AWG)
Posi-lock (18-24AWG) 
Tin Snips
Metal punch
2.5, 3 and 3.5 mm drill bit
3 x 25mm M3 screws
4 x 10mm M3 screws
13 x M3 nuts
Blue thread locker
Dremel (not necessary but comes in handy for grinding down rough and sharp edges).
Metal file 
(needed if no dremel)
CB125e bike manual
Electrical schematic for CB125.

Note: I have done this project on my own bike and it works perfectly fine. However, I am not responsible if you screw up your electrics, damage your bike or yourself in anyway due to the instructions contained in this instructable. You are responsible for your own actions on this project. Please take every precaution as safety comes first!!! You have been warned.

With that out of the way we now proceed to the actual project. Let's have some fun!!

Step 1: Taking Out the Halogen Bulb and Socket

For this step turn to pg 110 in the bikes manual. For those who have lost it refer to the above picture.

When you have removed the bulb from the headlight assembly, you will need to disconnect the molex power connector, unwrap and cut the wires that connect up to the light bulb socket. 

The wires that u have cut will be blue, white and green.

blue = low beam
white = high beam
green = ground

Knowing what these colours represent will be important. 

The white wire u can cut shorter then the others and heat shrink as it will not be used.

The headlight lens was also pried from the headlight body (see photo 2) using a small flat head screw driver.TAKE YOUR TIME and  BE CAREFUL as u can easily crack the lens.

Drill two 3 mm holes into the collar of the headlight assembly (terminal wires from LED will be threaded through these).

Step 2: Making LED Heat Sink

Like all high powered LED's this project will need a heat sink so that it doesn't fail prematurely. This is where the copper sheet and compass come in.

Using the compass measure out two circles with the diameter of 40 and 70 mm respectively. Once the circles have been drawn on the copper sheet cut out the respective circles with the tin snips. 
Procedure for 40 mm disk

The 40 mm disk of copper will be bolted onto the back of the LED assembly, while the 70 mm disk will be used to create a cover for the socket hole where the original socket went and to hang the LED assembly through said hole. 

Firstly in order to bolt the copper disk onto the back three holes have to be drilled. The LED light assemble comes mounted onto a base. This base has u shaped cutouts where the mounting bolts go. Mark out using black marker these cutouts (photo 1).

Once the bolt holes are marked out use a steel punch to mark the metal. Use the 2.5 mm drill to make a pilot hole before using the 3 mm (making a pilot hole first makes drilling the copper easier). The drilling of the copper will cause the copper to come out on the other side (see photo 3). Use the Dremel or a file to ground down flat (this deformation will happen to all the holes that you drill so u will have to grind or file them as well).

Now mount copper disk onto back of base and secure with M3 screws and nuts (use the blue thread locker to stop the nut from working free from vibration).

The assembly should now look like a circular disk with legs (photo 2).

Procedure for 70 mm disk

Placing the legs of the assembly on top of this piece of copper, centre it, and mark out with black marker where the drill holes for the legs will be (photo 5).

Use same procedure above to drill the holes . 

Once the holes have been drilled grab LED assembly, measure 12mm from base of assembly and place nut at that position.

Repeat for the other two legs (photo 6). Again use blue thread locker on the nuts to stop nuts from coming loose.

Insert the LED assembly through the socket hole, place the 70 mm disk on top of above screws and bolt down (as usual use blue thread locker on the nuts) [photo 7]


Step 3: Preparing LED

We want to run the 7 LED's in this assembly in series so that we only have to use one LED driver. In order to do this we need to place solder on the dots located from J!-J6 (see photo 1). 

Once solder dots have been soldered on , a red wire is soldered onto the +ive , a black wire is soldered onto the -ive terminal respectively. These wires are then threaded through the holes drilled in the collar in Step 1. (photo 2)

Step 4: Soldering Cap, Diode and Led Driver to the LED Assembly

Procedure for soldering cap and diode together

On one side of the capacitor u will find a -ive sign printed, this is the - ve side of the cap. You need to solder on the -ve side of the 1N5404 diode to this side (the -ive side is the side furthest from the white band on the body).

Then solder the +ive side of the diode (will have a white band on the body) to the +ive side of the cap (see wiring diagram).

Procedure for attaching LED assembly to driver

To get this procedure just follow the wiring diagram as it shows you how to connect the LED assembly to the driver.

NOTE: make sure you heat shrink your solder joints and the cap/diode to make it secure and limit it shorting out.

Step 5: Attaching LED Heat Sink Assembly to Headlight Body

The heat sink assembly was not glued into place since we still want to be able to remove it easily if we need to replace the LED. So in order to mount the LED assembly securely to the headlight body, we need to first make two L shaped brackets to hold the assembly in place. These brackets will be screwed into the collar of the headlight body.

Procedure for making brackets and mounting

Measure and cut a length of copper 70 mm x 15 mm, cut out using the tin snips and then cut the strip in half.

Measure out 20 mm then 15 mm on both strips (photo 1)

Drill two holes into the 20 mm side of the clip. Firstly drill a 2.5 mm pilot hole then a 3 mm hole (photo 3)

Transfer the holes onto the collar of the headlight body and drill the holes. When the holes have been drilled use epoxy to glue the nuts onto the other side of the collar (photo 3).

Screw the bracket onto the headlight body. 

Once mounted onto the headlight body bend the rest of the strip over.

Repeat above steps for 2nd strip,

Glue the khatod lens onto the LED assembly.

Reattach and glue the lens back onto the headlight body.

Step 6: Powering Led and Mounting Into Headlight Cowel

The power this project the power would be coming from the ignition wire. so the ignition wire had to be striped so that we could solder on a 50 mm wire. This 50 mm wire was striped on both ends, one was soldered onto the ignition wire, the other end had a posi-lock attached to it. The power cable on the project end was then screwed into the other end of the posi-lock. 

Make sure to insulate the joint with electrical tape so no moisture can get to it.

You are now done.

This an interesting little project that will take you a day or two to finish. Hope you have enjoyed this little instructable. It was my first so if you have any comments as to how to improve it please comment below. Any positive comments in fact are welcome :-)



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    2 Discussions


    5 years ago on Step 6

    Your title doesnt do the rest of your 'ible justice, I thought you were just going to replace the bulb, but this is a level higher.

    You should try to include the words, conversion, upgrade, led or similar in the title to more accurately reflect what you've actually done.

    Very nice headlight hack.


    5 years ago on Introduction

    I really like how you front-loaded the intro with the parts list as well as the rationale behind swapping out the weak halogens. My favorite reason was #4: "I love to tinker." This is a great first project. You even made excellent use of image notes, a sure sign of an Instructables prodigy. Looking forward to seeing what you get up to next.