GP125 electrical questions...

All to do with wiring, charging or just trying to figure out whats gone wrong.

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TFB
Still in the Driveway
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Joined: Sun Jun 14, 2020 6:12 pm
Country: Australia
Suzuki 2-Strokes: GP125 1980
Location: Perth, Western Australia
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GP125 electrical questions...

Post by TFB »

G'day all,

Hoping I can get a bit of help with my 1980 GP125 project.

I got the bike in a pretty basic state... a rebuilt motor which runs nicely, but no wiring loom or lights, etc. So I got a wiring loom from a 185cc Suzuki ag. bike, which seemed close enough to what my perusal of a GP125 wiring diagram showed. I also bought a Stanley rectifier unit (those simple little things with one wire in and one wire out).

Now it's all hooked up and running, the lights are working (except the indicators... waiting for those to arrive via eBay sometime in the next 6 years).

I'm a real newbie when it comes to magneto systems; I'm far more familiar with the 3-phase alternators of the GS/GSX Suzukis, but my knowledge there is of little relevance to the 6 volt electrical magneto system of my GP125. Soooo... my questions are:

1. Is it normal for the lights to be really dim at idle (tail light is almost flickering at the specified 1300 rpm) and really bright at a few thousand RPM. Like, so bright that the tail light almost could pass for the brake light?

2. There doesn't appear to be any voltage-regulating function in these electrical systems. Is this true? Or is there meant to be some sort of self-regulation of the voltage by some gizzardry in the magneto unit?

3. One thing the PO did supply with the machine was a regulator-rectifier unit he'd obtained from a wrecker/ breaker. I assume it's for a 6 volt system, but I have no way of really knowing. It has 4 wires: green, black, red, pink. Assuming it's compatible with the GP125 electrics, how could this be wired in to the existing system?

Thanks chaps and chapettes for any help you can offer.

Cheers, Mike.
GP125 1980
GS1000S 1979 (Yoshimura tribute)
GS1000G 1981
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jabcb
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Re: GP125 electrical questions...

Post by jabcb »

Suzuki didn’t sell that model in the US.

You should do research before running the bike with lights.
Suzuki used some rather “different” wiring layouts back then. Some bikes had a mixed AC/DC wiring setup with some items running on AC & some on DC. Some bikes use the battery as the voltage regulator. Some bikes have a resistor that is needed but seems to serve no good purpose. One little I-didn’t-know-that mistake & all of your lights could burn out.

Did you find an online parts manual for the bike?

Manuals & a wiring diagram for your specific model would be really useful. Check eBay. There is a New Zealand seller that sells manual reprints -- he might have them for your model.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
User avatar
TFB
Still in the Driveway
Posts: 2
Joined: Sun Jun 14, 2020 6:12 pm
Country: Australia
Suzuki 2-Strokes: GP125 1980
Location: Perth, Western Australia
Contact:

Re: GP125 electrical questions...

Post by TFB »

Thanks for that info. :up:

Unfortunately my bike came without most of the electrics... all it had was the coil and the magneto in the motor, the left and right switchgear, and that reg/rectifier which I'm 100% certain isn't part of the GP125's kit.

So as to what should be there... well, I do have a wiring diagram. Using the TS185 loom, I have been able to wire everything up the way it should have been... I *think*.

So if someone with actual knowledge of the GP125 could chime in at some stage, that would be great.
GP125 1980
GS1000S 1979 (Yoshimura tribute)
GS1000G 1981
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