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Minimalist Wire Harness for GL1500

4006 Views 11 Replies 6 Participants Last post by  satan
I have a 1992 GL1500 that I'm converting to a cafe racer. I'd like to pull out the existing wire harness and replace it with a harness that just runs the engine and gets all the lights working... I need nothing else. Does anyone have any suggestions on where I might obtain such a harness? Is there someone who makes custom harnesses for GL1500s? The current harness is quite massive and is way more than I need. Has anyone trimmed down a harness? Just looking for some ideas. I think the GL1500 cafe racer is an awesome looking bike and would like as few things hanging off of it as possible.

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Hey, someone finally getting around to stripping a 1500 around here. :)

You got a service manual, right?
What lights you plan on running?
Head/Tail/Turn? ...or just the head and tail?

Scan the wiring diagram in and start eliminating circuits, then redraw it. That way we'll all have one because I'm thinking you are the first to want one stripped, nekkid and skinny 'round here.

Get Ready and Good Luck.
You could pick up a Valkyrie wire harness
I've been in a similar predicament recently, restoring an old truck that had many "extra" wires, mostly from it having been converted from one type of engine to another.

I simply tested every circuits function, then began cutting wires one-at-a-time and testing all circuits again at every step. When I was done, I ended up with the Bare Essential Circuit and tossed the rest... From what remained, I ran new wires for lot's of it, and ended up with hardly any (unreliable) connectors, having replaced them with single lengths of wire instead.

I'd say that you could do the same with your bike.
Thanks for the input! I messed up with stripping the bike without taking my time and checking what I needed to run the bike as I unplugged stuff. Now, the bike has no spark. Not sure what I need to do to appease the engine computer gods to get her to run again. However, I love the look of a completely naked GL1500 - it just looks like a bad-ass cafe racer without doing a bit of custom work! So, once I get her running, I'll be all set.

Anyways, my next thought is to plug everything back in… get the bike running… unplug everything one at a time. The whole engine computer thing is throwing me off my game. I’ve built bikes before but they were old school and simple. I’m blown away with how much wire harness there is on a GL1500… it’s a bit overwhelming. Nonetheless, I’m dedicated to make this thing the coolest café racer in the neighborhood.

So… thanks for the thoughts! Once I get her running and all buffed up, I’ll post some pictures.
Stu... thanks for your thoughts! So, you think a Valkyrie wire harness will work? Will it plug into my current computer? All of this stuff is majic to me...

On a 1500 there really isn't much to get a timed spark... How much are ya loking for (just the ignition, or are ya looking for help with starting, running & signal lights, etc), and for what model (SE, INT)?

Just to get the ECU to support idle isn't too much at all (I'm working with an SE module here from a '93 - Hopefully you kept the plug ...cause wire colors are all I've got to go by). I'll arrange 3-sets of bullets here for ya as "ECU Power", "Timing Input", "Coil Output". there's a lot more to the ECU, but when you get this far, post back and we'll over the other sensors (for timing) and the solenoids (ACIV and Air Jets)... Cool?:

Get a little power to the ECU this way (don't connect the 12V until you're ready to start it up and you're certain that nothing is shorted to anything else...)
  • Solid Green wire goes to chassis/battery ground (ECU Ground)
  • Black with White stripe goes to 12V (ECU Power) - ignition switch!
  • Green with White stripe should go to a chassis ground (kickstand safety)
Let's try the bare-minimum (runs like poop) sensor wireing next
  • Green with Black wire is a sensor common line (NOT CHASSIS or BATTERY GROUND!), the "other" side of the sensors return on this wire...
  • White with a Yellow stripe wire is for the pulse generator White with a Yellow stripe wire (nice match, eh?)
  • White with a Blue stripe wire is for the pulse generator White with a Blue stripe wire (sense the trend?)
  • The solid BLUE and solid YELLOW wires (one per pulse generator) should connect to the Sensor Common wire (Green with Black stripe from above)
Then the coils - You'll need one connection that's NOT on the ECU for these:
  • 12V power enters all 3 of the coils on a Black wire that has a coil-specific colored stripe (these 3-wires at the coils all get +12v switched). You'll wanna kill power to this wire when the bike is off, and also ensure that there's minimal resistance in this wire. Plan on 15Amps -- often this can be relay switched using the ignition switch ;)
  • Each of the coils has a Yellow wire with a coil-specific color stripe. These Yellow striped wires will match yellow striped wires at the ECU. I believe that the coil-specific stipe colors are red, blue and white - good luck finding the Yellow wire with a White stripe... these will be easy at the coils (you can see 2 easy, the third wire is whatever is left-over). At the ECU these wires are all located close to each other on one end of the connector - so hopefully not too much difficulty.
That's all there is to a non-sensored, not-safed ECU... should be enough to idle until you run outta fuel in the carbs.

You can drive the fuel pump directly off the ECU by using the Black wire with Blue stripe (the ECU will switch this for ya, but ensure that the ECU +12V power supply & wiring is good enough to carry a few amps... 10A should be fine)

After you get this far, working the 2 temperature sensors, the gearshift sensor, and the solenoids should go easily - but it'll be best to idle first and move forward from there.

Let us know.
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Will it plug into my current computer?

No. It has a different brain box. Way less wires than the wing has for sure. More old school, I don't think there is even a sensor on the air box of the Valkyrie.
Satan! Wow! Thanks!

I'll dig into your instructions and see how far I get. I still have everything... so wire colors are good.


Once again, thanks! I have an SE. I'm pulling the stock tank and having a tank made that's gravity fed so I don't need to run a pump. So, everything that doesn't make the bike move forward or work the lights is coming off. I want as few things on the bike as possible.

Anyways, I'm going to follow your instructions this weekend and prepare for Phase II - the moving forward part. Can't thank you enough!

Thanks to Satan for stepping up and offering the help . This will be interesting to follow . Please do keep us in the know . Also sending out a big Hello and Welcome to the forum family .
This sounds to be great fun, and I wish I was closer to come and get my hands dirty.

To keep the 1500 running "right" you will need the gear position sensor, and I'd recommend keeping both of the temperature sensors also. (we can go over those when you've got idle). These are all used in the timing calculations; beyond that a simple decoder on the gearshift sensor for a "what gear am I in" display can be a "fun" bit of bling too...

Then the solenoids, of course...("Comp." solenoids if you look at parts fiche):
* The AICV Solenoid (controls the vacuum available for the actuation of the AICV, to dump fresh air into the exhaust's "Air Shot" system for backfire control)
* The Air Jet solenoids (these modify carb behavior)

Outside of the scope of "running engine" (and really something that could be part of the engine discussion), would be the reverse system, and if/how you wanted to run a tachometer...

This will be fun to watch.
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