My 75 GT550, electrical issues

[bobotech]

Engine is freed up and I am putting it back together.

Now to figure out what happened with the electrical back 30 years ago.

Here is what I'm starting with, a missing ignition switch (well half of one), a missing main fuse, and no power when I hook up a battery to the main cables.

First thing that I am attacking, the lack of the ignition switch. I went to my local recycler and they only could find a 4 pin plug switch. The factory GT550 has that 4 pin plug and 2 additional wires off of the switch. They didn't have one like that. I bought the one without those 2 wires jsut hoping that I could rig something up. Can I bypass those wires for now?

Where do you think I should start my troubleshooting?

[tz375]

Do you have a wiring diagram? If not, that's teh place to start. Then follow the power starting at the battery and follow it to teh ignition switch and out the other side to the kill switch and to the points and to the coils etc. In other words follow the path that the power is supposed to take and see if it's getting there.

Along the way you will probably encounter bad connections and rusty switches etc, but do it logically and follow from the diagram to the bike. It's just like following a ping trace to see the hops.

[bobotech]

Found this:

http://smokeriders.com/diagrams/Suzuki/ ... _GT550.gif" onclick="window.open(this.href);return false;

Do you know if this covers all the years including the 75?

[oldjapanesebikes]

The wiring diagrams typically are specific for the J/K models ('72/'73) . The only thing that really changed was the gear indicator display so with that caveat, yes - your model is covered.

[bobotech]

Okay, I got an ignition switch and I am in the process of testing.

This is going to sound stupid, but I don't even know what the 3 positions do on the igntion switch since mine was completely missing. Obviously, all the way counterclockwise is off, but I am not sure what the middle position is. Also I'm not sure what they mean by "ignition" on the far clockwise position means. If I put the ignition switch in the middle position, I hear a brief buzzing sound from under the battery and the only thing that works at all is the horn. If I put the ignition switch on the full clockwise position (ignition), I get nothing whatsoever.

I cannot find any decent wiring diagrams, they are all low resolution so when I try to blow them up to get a better feel of what is connected where, everything just turns to a blurry mess. Is there any high resolution versions of the wiring diagrams.

[jabcb]

SmokeRiders website has 2 GT550 diagrams:
http://smokeriders.com/diagrams/Suzuki/ ... r_GT550.gif (The one you found)
http://smokeriders.com/Technical/wiring ... grams.html (easier to read but not in English)
Another site also has the diagram:
http://www.ozebook.com/compendium/suzi/ ... T550wd.gif
Best bet probably is to compare the three to figure out what you need.

I have a GT550M owners manual. Its wiring diagram shows shows the 6 wires going to the ignition switch & also shows the gear indicator.

The GT380 & GT750 used the ignition switch with 4 wires:
http://smokeriders.com/diagrams/index.p ... /GT380.gif
http://smokeriders.com/diagrams/index.p ... /GT750.gif

The additional two wires on the GT550 separates out the power for the lights and coils. Suzuki presumably did this to increase the voltage at the coils when the lights are on.

Since your switch doesn't has the 2 additional wires, you won't be able to turn the lights on.

You should focus on getting the engine running. If you get to the point that the bikes runs and you are sure it worth fixing, then its also worth dealing with the ignition switch.

[tz375]

Start with what you have and let's work out how to make something work.

On the switch you have there are probably 3 or 4 key positions. Let's assume they are Off / Run / ?? / Park

In the ON position it will probably should two pairs of wires. One pair will be battery in and the matching wire will be switched 12V out to all the circuits. The other pair is typically tail light and the rest of the lighting circuit but that all depends on what it came from. On most triples that would be RED (battery) to Orange (switched 12v) and Brown(tail lamp) to Gray (instruments and other lights)

In the OFF position it's probable that nothing is connected.

In park it will connect battery to the Tail/park lights.

So we want to connect the battery lead on the switch to your battery positive (RED) and we want to connect the Switched 12V to the orange wire that would have been connected to the main switch in a perfect world. That will give you power to the ignition circuits starting with the kill switch and then to the coils and points.

It appears that on a 6 wire GT550, the extra two wires are RED 912v from battery) and the other lead goes to teh light switch which on Euro models appears to be Low-High-Pass. I haven't checked the US model but I suspect it's similar but without the Pass flasher button. The extra 2 wires appear to be a way to avoid pushing all the power through the ignition switch.

[bobotech]

Ahh! I think I understand now.

The switch has 3 positions, the leftmost position is OFF, nothing connected, the middle position is RUN, 2 pairs of wires are now activated, and the right position is PARK where 2 wires are connected to the parking lights.

Here is what I did, I used the remains of my 6 wire GT550 switch and merged them into the 4 wire Suzuki switch. Took a while but I got it working properly.

I think that the key positions on the switch I have are off, a dot, and ignition which is why I was confused.

Anywhos, I went ahead and hooked it up and was getting nothing but that buzzing sound. I then removed the voltage regulator and took it apart. I cleaned off the contacts with brake cleaner and checked the impedance, everything seemed okay.

Put it back on the bike and turned the key to the middle position and had power. I was able to hit the starter button and it spun the engine nicely. Had lights as well. Everything seems to be working.

Next up is to clean up the engine and clean up the points and hopefully I shall get spark.

[bobotech]

I translated that really good color wiring diagram for the GT550 and uploaded it to my photobucket account: