S2R 800 Bad ground? New taillight dim

[flanman]

Hi all! Hoping someone can point me in the right direction. I have had an integrated led tailight strip on my S2R 800 for a few years. It started getting dim so I bought a new one and hooked it up. When I use the black ground coming from the stock harness it is very dim (barely lit) but when I put the ground from the tailight to my exhaust it is eye scorching bright.

Also brand new Shorai (fully charged). There is no fuse or anything between the stock weather proof connector and tailight (should there be? I thought there was one before - maybe took it out by mistake when removing old led strip).

Any idea what is going on or where/what I can check?

Thanks! Sorry if this is a stupid question.

[ducpainter]

Sounds like the ground wire in the harness is compromised. You have choices. Fix the harness, or provide a good ground for the light. 

[flanman]

Thanks Ducpainter! Is there a spot where the harness is grounded (frame,motor?)

[ducpainter]

I'm more familiar with the first gen bikes as to the location of the ground points, there are several, but I suspect that the ground wire in the harness that goes to the taillight is bad as opposed to the ground points being loose, or dirty.

You can cut open the harness, starting at the light, and look for a broken/frayed wire, or simply run a new ground wire for the light and attach it to an existing ground point. I'd look at the ecu, or regulator/rectifier, for an existing ground. You can also go directly to the battery.

[Howie]

Best to run a new wire, and just use the ground for the alternator.  Opening the harness is messy.

Umm...scorchy brite?  You sure you didn't ground the brake light?