Converting a US Spec Headlamp to Euro spec (sort of) ( ST1100 ) *

[KoTAOW]

This article was taken from www.my-mc.com web page.  
It was originally submitted and written by Martin B. in August 2004.



Some of this work I did a number of years ago (therefore, I have no “before” pictures) and some of this work I did this weekend since I had all the bodywork off the bike anyway. I also took the opportunity to photograph the work as I didn't have a digital camera when I first did the work. What I intend to show is what needs to be done to modify a US spec headlamp housing to accept standard H4 bulbs and also how to modify the US spec housing to convert the beam pattern back to a European spec.



Photo Above: The entire lamp housing. I will be showing the left side.



Photo Above: Note the screw location at approximately 7 o'clock. Then note that there is an alternate location for that screw (and the clip) at 9 o'clock. That location actually exists on US spec housings but the hole is not drilled out and tapped with threads. (I’ve already done the work here in the photo.)

Now look at the clip retainer at approximately 2 o'clock. Note that it’s attached to the housing with it’s own screw and that the clip hooks under the left end of it. Now note that at the right end of the retainer there is a bent down corner. This bent down corner is what retains the clip after the clip is moved to its new location at 9 o'clock.

Finally, note that this housing has already been modified. Note the material that has been removed at approximately 5 and 7 o'clock. This will be shown clearer as we go on.



Photo Above: Note the areas marked in red. The red indicates where material has been removed to allow the two lower tabs of an H4 bulb to fit into the housing. (Sorry, no actual before photos.) Those two tabs on an H4 bulb are both lower and closer to the 6 o’clock position than the tabs on the 45/45 Honda bulbs. A flat ended grinder in a Dremel electric grinder can be used for this task. I used a dental laboratory grinder and bur. I also made a stop for the bur to more accurately control the depth of the slot as I widened it. As you widen each slot, take care to maintain the depth of the slot so that it matches the depth of the existing slot. The surface that supports each of the three tabs on the bulb is what accurately locates the bulb in the housing. If the new, widened parts of the slots are too deep or too shallow, the bulb will tilt accordingly and the bulb filament will not be in the proper location relative to the reflector. Note how the depth of the already cut areas in red are the same depth as the original slots for the 45/45 bulbs. Also note that a good portion of the boss and threads for the screw that holds the retaining clip in place have been ground away to make room for the H4 bulb. When determining how far to widen the slots, use an H4 bulb as a guide. You can hold it in position and use a fine point permanent marker to mark the housing. Also, some H4 bulbs like the PIAA’s use a narrow tab in the 7 o’clock position. For marking and grinding the housing, make sure you use an H4 bulb that uses a full size 7 o’clock tab. Otherwise, should you use a bulb with the narrow tab and modify the housing accordingly, you won’t be able to install a regular H4 bulb should you find it necessary to do so later.



Photo Above: One thing I didn’t do the when I first did this job was to remove the small tab at 6 o’clock. For some reason, on the H4 bulbs there are two tiny tabs that face forward. Probably some locating feature. But not having seen an actual H4 housing, I can’t say for sure. Up until now, I’ve just been bending and flattening these two tiny tabs so they clear the housing tab at 6 o’clock. Since I had the housing out this weekend, I thought why not remove that tab and avoid having to flatten the tabs on the bulb. So, the additional material removed is marked in red. Compare the photo above with the previous photo.

Once you’ve removed the material necessary to allow the H4 bulbs to fit properly, then you need to drill out and tap the new hole for relocating the retaining clip. In the photo above, it’s the threaded hole in the very upper left corner of the photo.

STOP! I should mention that you might want to try this part of the mod first. If for some reason you fail, you can easily put the retainer back into it’s stock location since you won’t have modified the slots yet.

The first thing you need to do to relocate the retaining clip is use a drill to make a hole where the new threads will be. Carefully measure the depth of the existing hole and don’t exceed this or you may find yourself with a hole on the inside of your reflector. Though, if this does happen, it’s probably not the end of the world as the reflector will likely still work just fine. Remember, the reflector housing material is some sort of plastic resin with what appears to be some fiber reinforcement. It will grind and drill easily. But, like plastic, I’m sure it’s possible for it to crack. Anyway, drill slowly and carefully. You can wrap some masking tape around the drill to make a temporary stop. And you might even want to do it by hand. Much slower but much safer.

Once you’ve got the hole done, you now need to thread it. I planned to use the stock screws and so I duplicated the basic hole ID and also duplicated the threads. Should you want to use a standard metric threaded screw, you should use as coarse a thread as possible and a thread OD as close to the original as possible. And, of course, use the correct pilot drill size and a bottoming tap. Another option would be to install a metal thread insert using epoxy or some Plastex or similar plastic repair material. Also keep in mind that should things get screwed up, these same materials can be used to fix things.

I didn’t feel comfortable just running the screw into the hole I’d just drilled because I wasn’t sure whether I’d split the plastic or not. So, I managed to find a screw in my collection with the identical thread diameter, pitch, and shape. (The stock screw looks similar to a self-tapping sheet metal screw.) I then ground some material off the end of the screw to make my own sheet metal screw tap. (Sorry, again no pix.) Using this, I carefully cut threads into the hole and ended up with threads identical to the stock hole. If you use a different screw to hold the retaining clip in place, remember that you’ll need a large diameter head or washer to properly retain it.



Photo Above: Now you can see the finished product. Note the lower tabs now fit into the red areas where the material was removed. And that the 7 o’clock tab interferes with the old clip retaining screw location. The original screw has been relocated to the new 9 o’clock position and the clip is now locked into place using the bent down corner of the clip retainer at approximately 2:30 o’clock.

The bulb shown here is a PIAA Extreme White 60/55 equivalent to 135/125. It has the narrow 7 o’clock tab but you can see that if I were to install a Phillips bulb (which I used to have in there), it would still fit. Also note that the two tiny tabs at the 6 o’clock position on the bulb base have been bent flat. I did this before I removed the tab feature on the housing. With the removal of that feature on the housing, flattening those two tabs on the bulb is not necessary.



Photo Above: Just a closer look at where the retaining clip now hooks. It’s quite secure and has never come undone. Of course, you’ll have to relearn how to undo and redo the clip but that’s relatively easy. When doing the final setup, make sure the end of the clip that hooks under the bent tab wants to spring towards the screw and not away from it.

Now you can use any H4 bulb in your housing without the use of adapters or modifying the bulbs. And, you can also use the Honda 45/45 bulbs should you need to. Don’t forget to thoroughly clean all the dust from the inside of the housing as dust on the reflector will reduce your light output.


This next modification is somewhat difficult if you don’t have the tools or equipment but I’ll show what needs to be done anyway.

From what I understand, the US DOT decided that the left beam on bikes needs to be cut off lower than the right. In the US, cars are also designed this way and it’s especially apparent if you’re running HID lights. While this makes some sense for cars and trucks where the lights are far apart and the left headlamp is close to the center line, I think it makes little sense on a bike where the lights are separated by inches and the bike can travel either in the left of right part of the lane. So, when I was cleaning the inside of the housing, I noticed the piece of sheet metal pop riveted to the top leading surface of the left reflector. This is what’s added to the European spec reflector to make it comply with the DOT regs. The two pop rivets seem to be aluminum and are therefore soft and easily ground away provided you’ve got a tool that will get in there. Since I have a dental laboratory handpiece and lots of different size grinding burs, I thought I’d give it a go. I almost couldn’t get in there but I was successful. Unfortunately, I forgot to take before pictures so you’ll have to imagine what things looked like with the plate in place. After grinding enough of the rivets away, the plate loosened and fell out. Of course, more cleanup of grinding debris was necessary. I was left with the remains of the two rivets still in the reflector, but with lots more reflective area exposed. So, unless I’m missing something, I now have a Euro spec lamp housing.

This picture shows the sheet metal plate that was riveted to the reflector along with the dental handpiece I used to grind the rivets:


This picture is a closeup of the plate:


This picture is looking in through the round opening for the bulb and shows the top of the reflector, a bit of the clear glass lens on the front, and also one of the remaining rivets:


This final picture is similar to the previous one but manages to show both remaining rivets with the now exposed bright reflector surface. Just like the surface on the right side of the housing:


I've just found out that the US and European spec headlamps may have different reflectors and lenses. So, while these mods may not result in an actual Euro spec equivalent headlamp, the mods are nevertheless an improvement over the stock US spec headlamp. Cheers all!

[KoTAOW]

Comment by Martin B:

I should point out again (I did so at the end of the article), that this work doesn't actually make a US spec housing into a European spec housing.  I thought so at the time but then I learned that the reflectors and the lens is different as well.  However, modifying it to accept H4 bulbs is a nice change for us DOT 45/45 owners and getting rid of the attenuator increases light output and I've not had anyone flashing me either.