"IF" you could provide us with some wiring colors on your aftermarket tail light.....that could help. (Are you sure your new light is a brake/tail light with two filaments in the bulb....and not just a tail light?).

Most STOP/TAIL lights that only have two wires use the body of the light for the ground.....this only works on light that are made of metal.  Generally the "red" wire is the brake light....the other wire is tail light....and the ground wire on the bike needs to be attached to the bolts that attach the light to the bike.

You can use the wire diagram to figure out which wire color on your bike is the ground (generally black and white dots).  The brake light wire is white with black dots, and the running light is brown).

So you would attach the black wire on the bike to the bolts on the tail light.
You would attach the white wire with the black dots to the red wire on the tail light.
You would attach the brown wire on the bike to the "other color" wire on the tail light.

savagerider87 wrote on 07/06/15 at 06:45:10:


Are you sure you bought a brake/tail light with 2 filaments?

Red is generally connected to positive, black is generally connected to ground when you only have 2 choices.

If the light truly is a brake/tail light....then I would connect the red to the brake light, black to the running light, and the housing to ground.

Can you provide a link to the light you purchased?

Says it is dual element...so red would be the brake light, black would be running light, and housing (bolts) are the ground.

Thank you guys! I really appreciate it!

Boogie_with_Stu wrote on 07/06/15 at 13:16:52:


Both available leads are for "hot" to come in.  One is to supply voltage to the running/tail light.....the other one is to supply power to the brake light.  The mounting bolt is the 'chassis ground".

If you have a battery charger and some wire, set the charger up, wires in the clamps. Negative, strip it back long enough to wrap around the base, or, clip the negative charger clamp straight on it, touch the wire from the positive to one of the buttons on bottom of the light, then the other.
Or, use an ohm meter. Learning this stuff is intimidating, but once you get it, you're gonna be shocked that you didn't understand. You hang in there, don't get impatient or discouraged.

Hold the bulb up and look. If you see two filaments, then one is brake, the other is turn.
Look at the stock bulb, see how it's wired, which filament gets lit up when you hit the brakes?
If the mounting bolts are the ground, make sure that they are grounded, not insulated by paint. You can even run a No Kidding ground wire from chassis to the mounting bolts.


http://www.elecdirect.com/catalog/crimp-wire-terminals

Or, solder a wire to a washer.. Buncha ways to skin this cat.

That's why I suggested running a ground wire from the mount bolt to a dependable ground.