Aftermarket taillight 2wires

I have an aftermarket tail light with two wires.  What do I do?

Not quite sure what your question is ?  Do you mean you have bought an after-market tail light & wish to replace the original unit? 

The two wires will be negative & positive - probably red for positive & black for negative.  Just work out which one is which & connect to the existing corresponding wiring on your original tail light.

But there are three wires to the bike, so is it just connecting black to black, red to white, and the brown wire just left dangling?

Is your existing unit combined with indicators ?

Or does it have a number plate light as well ?

One wire of the 3 on your bike will be for the brake/stop light live, the aftermarket light doesn't have this function so only has 2 wires, as Dave says one live 1 neutral. you could possibly take the bulb holder & wires out of the existing and transfer them to the aftermarket?

simbo wrote:

One wire of the 3 on your bike will be for the brake/stop light live, the aftermarket light doesn't have this function so only has 2 wires, as Dave says one live 1 neutral. you could possibly take the bulb holder & wires out of the existing and transfer them to the aftermarket?

good idea - I'm going to try this and hopefully it will work

Have you thought that maybe the earth runs through the mounting screws/bolts & consequently the 2 wires will be either a brake or tail light?