Thread: ORGS build up
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Old 05-15-2010, 12:26 PM   #34
x3300 OP
Joined: Mar 2005
Location: San Jose, CA
Oddometer: 170

I'll need a headlight, and I wanted something distinctive, something that said -- off-road.

I liked the the look of the big 8" race lights and figured I'd try to rig something up for street use. Both Baja Designs and Trail Tech make very similar products, an 8" light with a simple frame that attaches to the fork uppers with hose clamps.

I chose the Trail Tech light based solely on Internet photos. Both are so similar that I can't imagine one could be much better than the other. I'd like to hear from anyone who has compared them side-by-side.

Here's what arrived at my door.

This light comes fitted with a single filament 55 watt H1 bulb. This really isn't suitable for a street use headlight. After a bit of headlight study (see here) my idea was to fit a standard H4 (9003) bulb to the 8" shell. The H4 bulb is a dual filament bulb with an off-focus low beam filament and integral low beam mask.

I needed an H4 bulb holder to replace the existing H1 holder so I searched around at the local motorcycle wrecker and found what seemed to be a pretty common H4 light on older Honda motorcycles. The back shell is made of plastic and I figured it would be easy to cut down to make a bulb holder that could be glued onto the back of the 8" light.

Here's the junker compared to the 8".

I took a hammer and a pair of pliers to the Honda light to break away the front lens from the rear shell.

The H1 bulb holder on the 8" light is cast aluminum and held onto the shell by several bent over tangs and a bead of what seemed to be high-temp RTV silicon. I bent the tangs up and cut the silicon away to get the holder off.

Here is the H4 shell set on top of the 8" light.

Using a lathe I cut off the outer part of the plastic H4 shell then turned it down to a good size. Here's a comparison of the two holders with bulbs.

The drawing shows the bulb dimensions I measured:

    H1      = 27.0 mm
    H4 high = 20.0 mm
    H4 low  = 28.0 mm
The H1 bulb holder places the bulb about 5 mm behind the shell, so to get the H4 high beam filament at the same position that the H1 filament was I would need the base of the H4 bulb about 2 mm in front of where the H1 holder rests against the shell. Anyway, I marked out the cut with a Sharpie pen and started toward it on a bench grinder. I noticed the reflector mirroring started to peal off inside the bulb from the heat of grinding so I switched to a hand file.

Once I started getting close I checked the placement of the bulb by looking through the front lens at the reflection of the high beam filament in the reflector. Because of the reflector's parabolic shape it was easy to see when the filament was at the focal point.

Here's the filed down shell and my bulb holder ready to be glued together.

After all the grinding and filing there was a lot of metal and mirror junk inside the light that needed to be cleaned out. I started by just flushing it with clear warm water, then on the final fill-up I added a tablespoon of household ammonia to help reduce water spots. I was really surprised with the result. A very clean inside and only a few unnoticeable spots.

I got some Permatex Ultra Grey RTV silicon to glue the new holder to the shell. It seems to be very similar to what was originally used to hold the H1 holder on.

Here are a few photos that show the finished headlamp.

Here's the high and low beam patterns on a cardboard target a few feet in front of the bike. Both were taken with the same exposure settings.

The low beam pattern seems pretty good. I'll need to get the bike out of the garage to check how it looks down the road.

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