GN400 electrical comedy

[.Chris.]

Sorry if this is a bit noobish, electrics aren't my forte.

I'm trying to sort out the electrics on my GN400. It's one of those terrible 6v systems with no voltage regulator and direct AC lighting, the result being an extremely dim headlight at idle speed, getting less dim as the revs rise. Probably doesn't do the battery a lot of good, either, but I'm less concerned about that.

Here's a wiring diagram. The only difference between that diagram and my bike is that I cannot find the resistor wired between the horn button and lighting switch.

At present, it's all wired up as it should be, but the headlight is only just lit at idle, and doesn't get very bright even at 5000rpm.

As you can see from the diagram, the headlight is fed from the pink wire coming from the generator. This wire seems to have about 4.5v at idle, rising to about 20v at 5000rpm. If this wire is disconnected, the light goes out and the battery seems to stop charging. If the pink wire on the loom (i.e. the headlight feed) is connected to the battery, the light is lovely and bright, but obviously this isn't much of a solution as the battery would run flat fairly quickly. If the generator (and headlight) were connected directly to the battery, presumably it'd boil in fairly short order, so that's a no-no too.

So I'm wondering what to do - any ideas? One idea I did have would be to buy an aftermarket voltage regulator (or use one of the single-wire RXS100 ones I have lying around) and use it to regulate the feed coming from the pink wire, connecting it both to the battery and to the headlight. Hopefully the result of that would be a reasonable headlight and a charging battery.

Comments/help/derision welcome.
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Chris
1985 Kawasaki Z550F

[ZebraDriver]

You have checked to make sure its not a 12 volt bulb been fitted to your 6 volt circuit?

ZD

[.Chris.]

It's definitely a 6v bulb. I'm really confused as to why it lights so well when connected to the battery, but when the same wire is connected to the generator (which is apparently producing a very high voltage) it's very dim .
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Chris
1985 Kawasaki Z550F

[Timmeh]

Can you measure the resistance of the generator coils? As they age they tend to brake down, causing very high resistance and therefore no current.

HTH
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GSXR400 x2 | '94 RVF400 | '93 TZR125 4DL (again)
20:22:30 BLUEX5: i would love to be forced to undergo a**l plugging with different sizes
20:48:18 Temeluchus: comp you hunk of smouldering homos3x you

[.Chris.]

I'll do that later, thanks.
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Chris
1985 Kawasaki Z550F

[.Chris.]

Hmm, seems like the generator's a bit buggered. My multimeter couldn't give me a reading for their resistance (vs ground) - just gave the infinity sign. I'm therefore guessing you're right about the coils being shot and unable to provide enough current.

I do have a couple of spare engines, so I'll try swapping over either a complete engine or just the stator at some point. Westcountry windings do a 12v conversion for the SP370, which I would have thought would fit as it has largely the same engine, but it's £150 and I'm a bit broke at the minute.

Until then, I'm just going to connect the headlight feed (pink wire on loom) to the battery, and leave the pink wire from the generator disconnected. Looking at the circuit diagram this should be OK, as the battery is charged from the blue/white wire (either running through the big resistor or not, depending on whether the lights are on).
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Chris
1985 Kawasaki Z550F

[promufa]

[.Chris.]

Hmm, the coil-coil resistance was 1 ohm, so maybe it's not buggered after all . Thanks for the link, I'll take a look.
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Chris
1985 Kawasaki Z550F