So I have a '91 GS, and when I picked it up it had a hack-job wiring harness. None of the turn signals worked, side stand switch was gone, stock gauge lights were gone, no brake light, etc. My method to remedy this during it's "rebuild" before riding it for the rest of the year was to replace the wiring harness, so I picked one up off ebay from what now appears it may have been off a newer GS, much newer. A good chunk of the plugs, and wires are the same...however on the handlebar end of the harness I'm having difficulty figuring out what wire does exactly what and how I need to modify it.
(http://farm6.static.flickr.com/5291/5548111448_dce8bc521b.jpg) (http://www.flickr.com/photos/scott_schmitz/5548111448/)
IMAG0259 (http://www.flickr.com/photos/scott_schmitz/5548111448/) by schmitz516 (http://www.flickr.com/people/scott_schmitz/), on Flickr
(http://farm6.static.flickr.com/5015/5547523905_c94fae6881.jpg) (http://www.flickr.com/photos/scott_schmitz/5547523905/)
IMAG0260 (http://www.flickr.com/photos/scott_schmitz/5547523905/) by schmitz516 (http://www.flickr.com/people/scott_schmitz/), on Flickr
It appears the yellow one goes to the start/kill/brake switch, and the black is for the turn/horn/lights switch. Am I on the right track?
Also can anyone show me what a turn signal relay looks like? Mine appears to be missing, it looks to be a two prog plug in. And what about the side stand relay - as I don't have one?
Can't see all the wires or where that cable is going.
Your best bet is to look at the wiring diagram and check the wire quantity and color codes against the diagram. By the number of wires, it looks like the left handlebar cable or the instrument cluster. I think we need to know
* how many wires in it
* the color codes
* What year did that wiring harness come from?
The Haynes book has color coded wiring diagrams. A few colors changed over the years but most are the same. Also a couple connectors have changed the number of wires: the left controls, instruments and the right controls all have changed the number of wires from older bikes to newer ones.
You might check the diagram on the WIKI page
http://wiki.gstwins.com/index.php?n=Main.WiringDiagrams
Everything on my "F" is hidden inside the cowling and frame. Everything on my "E" bikes is stuffed inside the headlamp so unfortunately I can't see the connectors right now. Maybe someone with a bike that's not all together can readily tell you the connector purpose. It will still take the wiring diagram to sort it all out if your connectors don't match.
From the pictures of newer ones I have seen, connectors are wildy different (how many stages of wildly different, I don't know. At least 2, perhaps more.)
Going a lot newer, as you have, you get wires you have no use for - electonic tach, I think there's an extra wire in the pickup coil circuit, etc. and the connectors themselves are much different, though most of the wire colors are the same. I think that several things that are one-wire connectors on the old harness got lumped on the newer harnesses.
For my 1990, and probably for your 1991, the one on the wiki is the diagram that has worked for me - you just have to be aware of things like the US models not having a "sidelight" (or front parking light), though we do have the brown & white-black pair that feeds it where it is used. That diagram used to be available in a less abused format - the version on the wiki cuts off the label describing those lights.