You have voltage at the bulb socket? How did you check this?

The brake light socket, is it stock , did this bike originally use a regular bulb (non LED)?

 

I just checked it with a test like before coming to work today. My multimeter was in my box here at work. When I purchased the bike it had an LED light in it and I changed it out to a Tribar.

 

I`m thinking that the ground is suspect, because when you use the test light, you clip it to a good ground, bypassing the ground the light normally uses.

I`m looking at a wiring diagram for your bike, but of course it only shows the oem setup...

Make sure the black wire is secure in the terminals.

 

Thanks, I'll check it out when I get home and see how it goes.

 

I have running lights though, don't they share a common ground?

 

There is a ground wire coming from each lamp socket, they all merge at some point in there, but if the wire or connection is bad between the socket and where the ground wires merge, it will affect only one lamp.