Homemade Shift Light

As many Busa owners know, you can connect a shift light to the wires that control the "flapper" solenoid. Typically, the flapper solenoid is no longer used when the "small airbox mod" is done, and the function solenoid wires can be re-programmed for use as a shift light using ECU-Editor. I did this modification a while back and made a shift light with two LED's and a resistor. Although the two LED setup was functional, I was not happy with my design and I didn't want to pay $100+ that many of these lights can cost. So, I came up with an idea to convert a Harbor Freight 9-LED flashlight into a shift light. These are the flashlights that you can get in the two-packs for $1.99 or for free if you have the coupon. Here is how I did it:

Step 1 - Prepare Flashlight for Cutting:

Remove guts from flashlight, use the line next to the knurl as a cutting guide, carefully cut along the line with a hacksaw. Don't worry, if you are a little off on your cutting, you can fix this later, but try to make the cut as straight as possible.

Step 2 - Clean Up Cut and Prep for Wiring:

Now that you have made the cut, you can flatten out the cut surface and remove the burrs. Since my cut was on a slight angle, I used a metal file to flatten out the surface. After filing, I used a pocket knife to remove the burrs from the inside and outside around the cut. You will also notice that the light is cut off just above the top surface of the spring in the center.

Step 3 - Wiring:

Positive and Negative Terminals 330 Ohm 1/2 Watt Resistor with Wire Soldered to One End Resistor Soldered on Spring

I have identified the positive and negative terminals for the light. This is important, because LED's are diodes and diodes will not operate if the polarity of the power source is going in the wrong direction. The positive termination consists of the spring and the inner ring shown in the photo. The negative termination consists of the outer ring and the metal case of the light. The light originally operates on 3 x 1.5V batteries, so the voltage is 4.5V. We will be running the light at 12V, so there are a couple of things to consider. First and foremost is the correct operating voltage and second is the desired brightness of the light. Since the flashlight typically runs at 4.5V nominal, we will have to reduce the voltage to the LED's by using a 330 ohm 1/2 watt resistor. I soldered a piece of red wire to one end of the resistor and used shrink tube over the wire and the resistor. I left the other end of the resistor bare, so it could be soldered to the spring as shown in the photos. I then soldered a piece of black wire onto the negative terminal. The negative was a bit difficult to solder where the box is shown on the photo, because that terminal is touching the outer case (does not heat up enough), so I ended up soldering to the terminal just to the right, which is one of the leads from the LED. You can actually pick any of the terminals on the outer ring for the black wire, because they are all ground terminals.

Step 4 - Epoxy:

For this part, I used two part epoxy that we have at my work. However, you could use RTV, but it should be some type of electrical grade silicone. I used transmission gasket maker (black) RTV on a similar project and it worked very well. Here is what mine looks like with the epoxy:

For my diffuser, I used some two-part material that I had sitting around from another project, which I picked up at a craft supply store. I mixed a small amount of the material with yellow and red model paint to make orange. I thought that orange was a good color, because if you use blue or red, you might get pulled over by the po-po for having flashing lights on your bike. If I did not have this material, I probably would have just used paint, or mabe some dark window tint, or something similar. Whatever you use, you probably have one or two shots to get it right, so check the brightness. You can do this by touching the red and black wires to the positive and negative terminals on your bike or car battery. Despite adding quite a bit of this material to my light, it may be a little bright, but I want to try it out in the sunlight and at night just to see what it looks like when it's lit up.

Step 6 - Mounting the Light

Finally, you can see here what the new light looks like next to the old one (diffuser was not on in this photo). I used white Velcro to mount the light on top of the gage cluster. I plan on getting some black Velcro to make it look a little nicer. The last picture shows the light mounted and the orange diffuser.

Good luck with your project and I hope you find this useful.

BusaBob's Racing