modifying a motorcycle tail light...

Discussion in 'Electrical' started by RedBaronX, Aug 24, 2011.

  1. RedBaronX

    RedBaronX Member

    Modifying a motorcycle tail light... This light is designed to run at one brightness as a running light and then at a brighter brightness as a brake light... if I were using a motorcycle wiring harness, I am sure it would be wired up to work like that, but I am building my own system. That means I am adding LEDs to be the running lights while the bright center light will be the brake light (I might even adde a relay to make it flash, but I haven't decided). The yellow piece of plastic is actually a cut-up DVD case painted yellow and will fit inside beneath the bulb. (if I had been thinking, I would have used a white DVD case, but I JUST thought of that... I guess I still have time to change that...)


    I am going to mount this to the rear fender with a bent corner brace, and there will also be turn signals-- I just finished painting the chunk of PVC pipe that they will be sprouting out from.

    The brake light switch is built in to the brake lever I am using-- I think it is off of a 1970's Yamaha (eBay). Using a generic motorcycle switch unit that controls headlight, turn signals, and horn.

    more pictures to come as things get assembled (I can't find the rest of the LED lamps, so I have to order more before I can complete the LED panel that gets fitted into the tail light... I am sure I will find the missing ones an hour after I place the order for the new ones...)

  2. IbedaYank

    IbedaYank Member

    they do sell 1157 led bulbs are some on ebay
  3. RedBaronX

    RedBaronX Member

    I got the bulbs I have from eBay in the first place, and they came in a pack of twenty... I just can't physically find more than those six in my house right now, and I don't know where the rest went... :-/

    I've ordered more... but I am still hoping to find the rest of the ones that I do actually have... somewhere around here...
  4. 2strokepoke

    2strokepoke Member

    well thats a bummer you misplaced those LEDs but once you get it all together it should be pretty sweet :)
  5. IbedaYank

    IbedaYank Member

  6. RedBaronX

    RedBaronX Member

    that is the very bulb that I am using in the existing tail light socket, but I don't have the wiring to brighten it and dim it as I apply and release the brakes. So, the LEDs I am adding will be wired to be the running tail lights and the existing bulb will be wired to the brake light lever switch (still thinking about adding a flashing relay)
  7. Big Red

    Big Red Active Member


    I used a motorcycle control unit on the last trike I built. It worked out great. I also hooked up the choke cable lever to the carb so no more choke vibrating into the CHOKE position.
    Big Red.
    Last edited: Aug 26, 2011
  8. RedBaronX

    RedBaronX Member

    I'm just going with what I know... I'm also thinking of adding another light fixture, something that will ride higher on the fender (there is a spot and hardware for a reflector). If I add in another fixture, I can decide to make that an additional brake light or make that a flashing running light... without having to "redesign" what the wiring is going to be... it's more wires, but it's not more designing...
  9. IbedaYank

    IbedaYank Member


    the dim is running/headlight circuit
    the bright is brake light circuit
    nothing is being dimmed
  10. IbedaYank

    IbedaYank Member

    led bulbs do not work with a standard flasher ....
    not enough draw to heat the element inside the flasher to make them flash

    to make brake light circuit work use a Ebike brake lever with the switch in the lever
    much cheaper then using honda moped levers

    if you need it i can hunt down a wiring diagram for you to make it easy
  11. RedBaronX

    RedBaronX Member

    OK... there are two nodes on the bottom of the bulb. There are two wires that connect to each of those nodes... When I touch either of those wires to the positive connection of the battery I have-- nothing happens. When I complete the circuit by touching a wire to the side of the bulb and back to the negative connection of the battery, the light comes on-- BRIGHT. NO matter which of the two nodes on the bulb I touch it comes on at the same intensity. Maybe that isn't how it's "supposed" to work, but that is what I have.

    That is why I am modifying what I have by adding a second set of LEDs that will be running on their own circuit.

    And I already have a brake handle with a brake light switch. Bought it about a year ago. But that's a useful link if for some reason the switch I have fails (it IS used.)
  12. IbedaYank

    IbedaYank Member

    side of the bulb is negative
    one lump will be running lights the other will be brake/turn
    best way to tell would be to use jumper wires one will out shine the other thats the brake light side
    if give me a about half hour i can tell ya witch is witch on a standard bulb
    there is 2 little metal studs on the side of the bulbs that are at differnt heights
  13. IbedaYank

    IbedaYank Member

    ok...looking at the bulb with the shorter of the studs that hold the bulb facing you the brake light element is the one to the left
  14. RedBaronX

    RedBaronX Member

    one stud isn't SHORTER, but one is definitely closer to the bottom of the bulb...

    and in my not-terribly-scientific test (turn on the bathroom light, connect one configuration to the battery, shut off light; repeat with other configuration) they look like the same brightness... (the bulb is 20 something individual LED lamps, and they all come on at the same time with both connections)
  15. IbedaYank

    IbedaYank Member

    yeah thats what i mean by shorter
    what did you use to test the light?
    regulated power supply or FULLY charged battery?
    remember a led is a light emmiting diode
  16. RedBaronX

    RedBaronX Member

    like I said, I'm going with what I have and what I know... battery + wires + lamps = tail light. I don't have a regulating power supply...
  17. IbedaYank

    IbedaYank Member

    this is what i do for work...boss hates wiring bikes as in motorcycles mostly pre 1975 british

    regulated power supply is just something like a battery charger but puts out 13.8 volts dc and plugs in the wall..... very usefull for testing 12 stuff without the need for a battery on your bench
    its all switches bits of wire and bulbs just used in the right order and places