Generator Question

I had mentioned in a previous post that when riding, the voltage gauge was only showing about 12.5v. Last weekend, I checked out the battery and it was a little low on fluid so filled up and charged and was all good. Rode around for a week, no issues. By Friday while cranking you can hear the battery struggling to get the bike started. Pulled it when I got home and attached to charger and it was showing 11% life. Charged up 100%, reinstalled and its doing the same thing again.

Voltage gauge (as well as voltmeter) with fresh charge shows a solid 12.5v or so when off. While riding, it goes from just under 12 (about 11.8v) to about 12.8. So obviously, the bike isn't charging itself well and keeps draining the battery because of it. I looked over the wiring and from what I can tell it's all good. If the generator wasn't connected properly, I would assume that the battery would die long before then what it's doing.

So the questions... I don't really know how the generator works on the bike, so could it be dirty or having issues making the charge? Or does it sound like it may just be bad? To the best of my knowledge, it has never been replaced.

Thanks!

You will need to get your hands on a Kawasaki Service Manual. They usually are available on eBay; just be sure to get one that covers your bike's exact year/model. They are worth their weight in gold. In it you'll find instructions for testing the bike's charging components. It is very possible your regulator/rectifier is not operating properly even if your generator is, so testing that would be a good place to start. I don't know of an online version of the manual for the GpZ750 or I'd give the link; maybe someone else knows of one. Ed

The charging system is almost exactly the same as on the 81 and later 550, so if you can't find a 750 manual online, you could look through the several I have for the 550 to get some idea on how to do the testing.

There is a misprint in the 3rd party manual. 1-phase stators should get up to about 75 VAC, and 3-phase will get around 50 to 60 VAC on each pair. The manual might have the numbers swapped.

I would first check the factory manuals, though.

I would first do an ohm test and ground test on the three yellow wires in case one of your yellow wires is broken or shorted under the sprocket cover.

You can download a factory manual here
mbsween.bike-night.com/kz750l3/manual.html
courtesy of mbsween who is member of KZR.
Also scroll down for complete wiring diagrams
Good luck