Vintage Motorcycle LED Conversion

About: My name is Matt; I like making stuff, and retro tech. I'm not a professional engineer, I just play one on TV.

I wanted to convert my 1974 motorcycle lighting from the increasingly rare 6 volt system to an all LED system. This article focuses on the turn signals.

**NOTE** Some may notice I neglected to include a resister. I had plan to place it elsewhere in the harness, but I may just integrate it into the signal housing later (recommended). I also recommend using something more durable than cardboard to secure the LED in the signal's socket (step 9). I just use it because it was what I had on hand at the time; I'll be changing that later, too.

**ALSO** This is my first instructable, so if something is out of place, forgive me.

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Step 1:

Here is the signal we'll be working on today. This particular lamp has two screws holding the lens to the signal body.

Step 2:

After the lens has been removed, you'll find the ancient 6v bulb snugged into the housing. Now would be a good time to remove the bulb. (I kept it in to explain the next step.) You may notice the bulb appears dark, or dirty. This is usually a sign the bulb is near the end of it's life. In most 6v systems, once a bulb blows out, it usually snowballs until they are all blown out. You'll want to remove the three screws holding the rubber bulb housing in place. Take note of the grounding wire held in place by one of the screws, take care not to damage this.

Step 3:

Note that the grounding wire is soldered to the base of the rubber bulb housing. This connects to the side of the bulb and grounds it through the body of the motorcycle, while the live wire makes contact to the bottom of the bulb. This completes the circuit and illuminates the bulb. We will be using the same concept to light the LED.

Step 4:

For this step, you'll need to clip the live wire and pull it through the signal body. Be sure to cut it so you have enough wire on both halves, should you need to reuse the connecter. For my specific application I do not need it, but I still like to give myself the option in case something changes down the road.

Step 5:

Now that the rubber housing is removed from the signal body, we begin to see just how simple this is set up. If you have not removed the bulb, do it now.

Step 6:

Now pull/push the live wire through the rubber housing along with the tension spring and plastic spacer. You will no longer need these parts, and may discard them now.

NOTE: Do not remove the original grounding wire, you will need it later.

Step 7:

Now, choosing a wire small enough to fit through the shaft of the signal body, cut a piece with plenty of length to travel through the shaft and out the housing. I cut enough to have about fifteen inches outside the shaft. This insures I have plenty of wire to work with later. You'll also need a smaller piece to attach to the grounding wire.

Step 8:

Now the fun part. Solder the live (longer) wire to the anode (positive lead) of your LED, and the ground (shorter wire) to the cathode (negative lead) of your LED. Go ahead and check the connections before shrink-wrapping. After that, go ahead and shrink-wrap the individual leads.

It isn't necessary, but I also shrink-wrapped the two leads together.

Step 9:

Now we need a way to keep the LED from shaking all over the place inside the signal body. All I had on hand was some cardboard, but i'm going to go back and use some heavy duty rubber, and glue it all in. I just needed something temporary. For now, you get the picture.

Whatever you choose though, it needs to fit snug inside the space the bulb use to take up.

Step 10:

Take a moment and check that everything is still working right.

Step 11:

Finally, solder the grounding wire from the LED to the original grounding wire.

Step 12:

Insert the three screws securing the rubber housing to the signal body. Make sure the screws are snug to insure a proper connection to ground.

Step 13:

Success! With the live wire connected to a power source, and the body grounded, the LED fires perfectly.

Once again, you're going to want a resister somewhere in the loop. I'll probably go back and put one in-line with the live wire. Keep in mind each application is going to be different. This signal is off of a 1974 Suzuki, but I imagine the concept is similar across the board.

Good luck!

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    12 Discussions


    3 years ago

    I like that you chose this route, but you can get bayonet type bulbs that fit in the old incandescent sockets, so you only have to add the resistor, they're already bright enough. Though, if you got rid of the old flasher relay and replaced it with a simple two transistor flashing circuit there'd probably be no need for the resistor.


    3 years ago

    Try to make a you tube video for other people to benefit from this as i was thinking a while ago to do exactly the same thing since i dont see any better solution


    4 years ago on Step 13

    Great instructable. I have to agree with the comment below about using more LEDs. I am not sure a single LED would be visible enough to see during the day. I think using multiple LEDs would do the trick.


    4 years ago on Step 13

    thats great do you know can you use more LED's instead of a resistor and or what resistor do you use ?


    5 years ago on Introduction

    this is a great instructable, I had the same issue on my 1982 suzuki but a site has 6v led replascement bulbs for automotive lights I haven't found a really good option for the headlight other than adding an auxiliary light

    Nice job.

    You might want to remember that old style blinkers relied on enough current flowing through the bi-metal blinker in order to make it work correctly. You may need to make a solid state blinker circuit in order to get things working correctly again. At least in '74, the turn signal switch was manual on/off, so it should be easy enough to make a 555/556 based circuit do what you want on 6 volts.

    Is the LED light as bright as the old incandescent one? Seems to me you might need more LED's to make it up to snuff for inspection. More LED's will also help in drawing more current through the original blinker, maybe enabling you to retain the original circuit.


    4 replies

    WOWWWW you know your stuff... I have the same motorcycle, and need to do the same thing.... how would i wire the light including more leds? also what resistors for the 6v current? and should i do parallel wiring? so many questions!!!

    Sorry it took so long to get back to you, but life has been really busy.

    The easiest way to learn is to look at some of the on-line calulators. Try this search. one that popped out at me was this one. It will let you put in all the necessary info and design an appropriate circuit with 3 possible graphic outputs: ASCII, Schematic or Wiring Diagram. Choose the type you need or keep switching between to see what works best for the situation.

    Good luck with your retrofit.


    thanks for checking out the article. You raise good points, i didnt want to stray too far away from the main topic, but im using an arduino to power the lights (as well as other functions, engine temperature readings, fuel and oil levels, etc). i also thought about using a 555, but tieing the lights to the arduino helps keep everything all together (for me anyway).

    as far a brightness goes, these things are bright. almost too bright to where if you catch the angle just right, it hurts a little. im actually going to have to either sand down the top of the led, or dab a bit of silver paint over it.

    It's good to see a retrofit of new tech with the old. I see the arduino in the opening pic now.

    The directionality of the LED is what had me concerned about the brightness. You need to have as much of the lense lit as possible. Sanding the LED lense or a dab of chrome paint on the end similar a Halogen bulb, something to diverge the light.

    I'd like to see the finished result. Here's to then!