Retrofit a Honda scooter headlight for halogen bulbs

Honda Scooter Headlight

When restoring my Aero 125 (a.k.a. NH125 or Lead 125), I found that the low beam was burned out in my headlight (Part #33120-KG8-670).  I soon discovered that these headlights haven’t been made for years, and there are no new ones available.  Used ones are selling on eBay for near $100, but these are coming out of trashed scooters and are destined to burn out soon.  So, I decided to retrofit the headlight assembly to use modern, replaceable halogen bulbs.

While these instructions were made for my Aero 125, they also will likely work for similar, older scooters with sealed beam headlights (e.g. Aero 80, Elite 125, etc.).  Your mileage may vary.

There are a lot of high-resolution photographs in this document so that you can see each step along the way.  Simply click on any of them to see the high-resolution version.

Choosing the bulb

When selecting the replacement bulb type, I wanted one that was cheap and readily available. It also has to match the current drain of the original headlight which is 35 watts for the high beam and 35 watts for the low beam.  I decided to use the T4 base 35w/35w bulb which can easily be found for around $5.  Just google “T4 35W halogen”.  Here is what they look like.

Bulb in package
Side view. Notice the two filaments – one for the low beam and one for the high beam.
Top view. Notice the lowest tab is bigger than the other two. That tab goes to the top of the headlight.
Bottom view. Notice the three electrical connectors – one for ground, one for low beam, and one for high beam.

You will need to buy the bulb first because you will use it to make the connecting socket on the back of the headlight.

I recommend you purchase at least two bulbs.  You have to be careful working with them to insure you NEVER TOUCH THE GLASS part of the bulb.  The oil from your finger will weaken the bulb when it gets hot and it will die a quick death.  If you have two bulbs, then you can use one as the sacrificial bulb so you don’t have to worry about touching the glass when you are getting everything built to match it.

I bought mine from REALHOG.COM for $5.50 each with free shipping.

Part # EIKO-48220-BP

You will also need a new socket for the bulb.  I found a very nice right angle, ceramic (high temperature) socket that fits perfectly in the scooter.  You must use a right angle socket because there isn’t much room behind the headlight.

Right angle, ceramic socket for a T4 bulb

I bought mine from

Part # Socket , Color: H4 Ceramic (90 Degree) , Type: Pigtail

Removing the old light source

First, start by removing the headlight assembly from the scooter.  There are two large bolts on either side of the headlight that are removed to remove the headlight assembly.  Don’t remove the Phillips screws.  These are for adjusting the headlight beam.  After removing the bolts, you need to remove the electrical connections.  Be sure you keep track of where you disconnected each wire from the wiring harness.  I used a sharpie marker to mark the correct locations.  When you have removed the assembly, it should look like the picture below.

Honda scooter headlight assembly
Headlight assmebly – side view

Next, remove the headlight from the assembly.  To do this, you need to remove one of the adjustment screws – the one that is physically attached to the bulb itself.

First, remove the rubber cap on the back of the screw.  Then remove the screw.  Put the screw, spring, rubber cap, and white nut into a zip-lock bag so you don’t lose any of the parts.

Remove this adjustment screw to remove the headlight from the assembly
Headlight has successfully been removed from the assembly

Now it is time to remove the old light source.  If you look carefully, you will see that the manufacturer simply soldered in a two filament light bulb into the back, metal reflecting case and then glued a glass lens on the front.  We will unsolder the bulb and then break the bulb to remove it.

To unsolder the bulb, you will need a very hot soldering gun.  A soldering iron will not even come close to working.  I used my Radio Shack 230 Watt soldering gun.  They aren’t very expensive and you need the right tools.  You will also need a pair of vise grips to hold the bulb.

The tools you will need to remove the bulb

Grip the bulb with your vice grips and then start moving your hot soldering gun around the base of the bulb.  As the solder melts in an area, it will drip off leaving less solder.  Be careful not to drop hot solder on you, the floor, or your shoes.  Work over an old board or something similar.

Removing the solder

Once the solder is removed, the bulb will move freely.

Bulb is loose

Now we need to remove the light bulb.  The manufacturer put it in through the front of the metal reflector.  We can’t take it out of the front because the glass lens is now glued onto the metal reflector.  So, we will need to break the bulb without damaging the headlight enclosure.

To break the bulb, simply adjust your vice grips a little bit smaller and clamp down tightly on the base.  The glass will shatter inside the headlight enclosure and the filament part can be easily removed.

Filament is removed from the headlight

Now, just shake all the broken glass out of the headlight enclosure.

The remains of the broken bulb
The two filaments of the broken bulb. Notice that one is open (a gap in the filament).

Installing the new light source

The next step is to modify the headlight enclosure to accept our new halogen bulb.  The old light bulb is slightly smaller than the new halogen bulb base, so we need to make the hole larger.  After we have enlarged the hole, then we need to attach mounting tabs that will hold the bulb in place.

First we need to enlarge the hole.  I used a Dremel tool with a grinding stone attachment to do the job.

Dremel with grinding stone ready to do the work

If you look carefully, there is a small lip around the opening.  We first need to remove the lip.

Small lip around the opening
Small lip is now gone

Next, place the halogen bulb through the hole and mark the edges with a sharpie marker.  Grind the hole larger to the edge of the sharpie marker.  Work carefully to ensure you have a nice, round hole of exactly the right size.

Hole is now round and the correct size

After you finish, your grinding stone may look like mine.  Time to get a new stone.

Grinding stone after making the hole the right size

Next, it is time to attach the mounting tabs that will hold the bulb in place.  This was the hardest part of the project because there isn’t really a great way to hold the tabs while the adhesive dries.

I cut strips of sheet metal and then bent them into the shape I needed.  Then I used JB Weld to attach them to the back of the metal enclosure.  JB Weld can withstand high temperatures and is a good epoxy based adhesive that attaches well to metal.

First cut strips of sheet metal to about the width of the height of the tabs on the T4 base.  Then bend it to make a tab that can be used to release the bulb when you want to install a new one.

Cut strips of sheet metal and then bend to make a mounting tab
Side view of mounting tab

The long part of the tab will be curved to match the shape of the metal reflecter.  You will make three of these – one for each tab.  I found it easiest to tape the halogen bulb in place with electrical tape so that I could measure the tabs as I made them.

As mentioned earlier, we are using a T4 base halogen lamp.  It is very important that the bulb be oriented correctly in order for the high and low beams to work properly.

T4 base halogen bulb

The bulb needs to be oriented into the headlight so that the large tab is at the top of the headlight enclosure.

Be sure the large tab is at the top of the headlight

Put the bulb into the headlight enclosure with the bulb oriented correctly.  Fasten it in place with electrical tape. Note that in the pictures below, I also connected the right angle ceramic socket because I wanted to hook it up to a battery and see how well it worked!

Bulb taped in place on the back of the headlight enclosure
Another view
Yet another view

Now you can make sure that the tabs will fit as you make them.

Be sure to put all of the long parts of the mounting tabs pointing clockwise so that you can twist the bulb to remove it and replace it.  If you have some tabs pointing counter-clockwise, then you can’t replace the bulb because it won’t twist.

You also want the tabs so that they are tangent to the round part of the base.  If they aren’t tangent, then they either won’t hold well or will put too much friction on the bulb when you try to remove it.

Once you have made all the tabs, use electrical tape to hold them in the right place on the back of the headlight enclosure.  I decided to attach the tabs in two steps: first gluing the part closest to the spring tab and second, gluing the long part of the tab.  So, I taped the long part of the tabs so that I could JB Weld the part closest to the spring tab. I cut away some of the electrical tape so that the glue would hold the tabs to the metal.

Now it is time to attach the tabs to the headlight enclosure with JB Weld.  Mix up a batch of it.  I have found that the most common mistake with JB Weld is not mixing it well enough.  BE SURE TO MIX THOROUGHLY.  After you have mixed the JB Weld thoroughly, mix it some more.

Now apply JB Weld to the tabs.  BE SURE to keep the area directly around the hole clear of JB Weld.  The base of the halogen bulb will rest here and it needs a flat surface.

Electrical tape holding the tabs while JB Weld dries
Another view of the tape holding the tabs

Once the JB Weld dries, you can remove the electrical tape.  Simply stretch the tape and it will slide out of the JB Weld in the areas where the glue went over the tape.

Stretch electrical tape to easily remove
Remove electrical tape after stretching it

Now, use another batch of JB Weld to glue the back of the tabs.  After the JB Weld dries on the back of the tabs, I mixed up a third batch of JB Weld and covered the whole thing again, just to make sure there is enough strength.

Here is what it looked like when I was finished

Finished headlight enclosure with tabs glued in place

The tabs are holding the bulb in nice and tight. There is no movement of the bulb, but it can be removed when necessary.

Electrical wiring

The last step is to wire the T4 ceramic socket into the scooter.  I decided to use the wire from the old bulb and solder it to the new socket.

First, I cut the wire from the old bulb.

Cut the wires from the old bulb

Next, I trimmed up both the old wires and the new wires on the socket.

Wires all trimmed up and ready for soldering

Next, I put heat shrink tubing on the new wires so after we have soldered the wires, we can properly insulate them.  Remember to put the heat shrink tubing on before soldering.

Heat shrink tubing is on the new wires

Next, we simply solder the old wires onto the new socket.  You don’t need a soldering gun for this part, a nice soldering iron will work better.  Use proper soldering technique so you don’t have a cold solder joint.  If you don’t know what a cold solder joint is, find someone who can teach you how to solder.

The new solder connector wires are black (ground), red (low beam), and blue (high beam).  The old wires are green (ground), white (low beam), and blue (high beam).

Wires soldered

Now we move the heat shrink into place and heat it up to insulate the wires.

Wiring completed

Now, doesn’t this wiring look nice!

Reassemble the headlight

You now have a headlight enclosure that accommodates an inexpensive T4 halogen bulb that matches the current draw of your old headlight.  You also have a connector that is ready to be wired into your scooter wiring.  All that is left to do is to put everything back together.

Start by putting the headlight enclosure into the headlight assembly.  Then reconnect the wiring to your scooter.  Next, put your halogen bulb into the headlight enclosure and attach the right angle ceramic socket.  Finally, replace the headlight assembly into your scooter.

You now have a functioning headlight that is ready to be adjusted.  After adjusting, you are all ready to ride!

If you found this article helpful, please leave a reply below.  Thanks!

2 thoughts on “Retrofit a Honda scooter headlight for halogen bulbs

  1. How is the beam pattern? I have a very similar headlight fixture in an 87 Yamaha Jog. I put the same bulb in, the low beam pattern is acceptable, but the high is unusable. How was yours?


    1. It is surprisingly good. I was most concerned that the beam pattern would be unusable, but after installing the bulb and testing it against a wall, the low beam was even and low and the high beam was even and approximately the right height.

      You might try rotating the bulb 180 degrees to see if the high beam will reflect better. You also make sure the bulb is in straight, but you probably already have done that.

      Good luck!

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