Voltage Regulator --->>> ~15.2 VDC @ 4000 RPMs

1981 KZ650-CSR w 3-phase alternator (3 yellow wires) & regulator/rectifier combo unit.

Checking the voltage at the battery, I'm getting ~12.6 VDC at Idle & ~15.2 VDC @ 4000 RPMs --->>> is that considered too high? The manual says it should be "about" 14.5 V. Thanks.

It's only very slightly too high. My Kawasaki Service Manuals which cover KZ650 models from '77 - '80 call for "14 - 15v" at 4,000 rpm. Ed

martin_csr wrote: 1981 KZ650-CSR w 3-phase alternator (3 yellow wires) & regulator/rectifier combo unit.

Checking the voltage at the battery, I'm getting ~12.6 VDC at Idle & ~15.2 VDC @ 4000 RPMs --->>> is that considered too high? The manual says it should be "about" 14.5 V. Thanks.

I had that on 2 of my KZ's, ruined one battery from it on a long trip. Found the Voltage sense wire to the R/R had a Voltage drop, and the R/R was making up the difference. One I got rid of the voltage drop, charging was back in the mid 14 volt range. 3 years later and the same battery is fine, and I've done lots of long trips on it.
Measure the Voltage at the battery, across the terminals with Key on, then at the R/R plug Brown Wire. See if has much of a drop.

Trouble shoot R/R/charging circuits no doubt for piece of mind...

Meter deflection/How accurate is your meter....?

Test on your car while running, normally would see ~ 13.8Vdc on the alternator (with internal regulation)...

If .5Vdc higher then expected 13.8Vdc, know your meter is reading high...

What's the measurement with lights/accessories on...?

Just a thought...

Old Man Rock wrote: Trouble shoot R/R/charging circuits no doubt for piece of mind...

Meter deflection/How accurate is your meter....?

Test on your car while running, normally would see ~ 13.8Vdc on the alternator (with internal regulation)...

If .5Vdc higher then expected 13.8Vdc, know your meter is reading high...

What's the measurement with lights/accessories on...?

Just a thought...

I test lots of charging systems, and get 14.2 or so regularly when testing a Vehicle.
Fully charge your battery, take the surface charge off by turning the headlight on for 20 seconds. Then let it rest for a hour and measure battery voltage. Should be like 12.6 if its good, there is a chart somewhere on KZR already or do a google search for 12v battery test voltage.

Thanks. I'm using a VC97 digital multimeter which is pretty accurate. The battery is new and was properly serviced & charged prior to installation, but I haven't done the high beam test on it yet. I'm getting normal voltage at idle.
Should I check the brown wire at the regulator, or can I check it anywhere?

Side note. The manual for a modern ZX10 says the charging voltage should be 14.2 - 15.2 (depending on engine speed) but not higher, so I was wondering if those numbers would be acceptable for any bike - aren't they all pretty much the same in regards to the charging system? I read somewhere that there is one company in Japan that makes all of the voltage regulators -- from looking at a good number of Kawasaki R/R that seems to be true, in regards to Kaws anyway.

You should check the Voltage at the R/R plug on the brown wire to see what that voltage is compared to the battery. If it is low/ a drop, the R/R will make up the low voltage. So if you have 15.2 volts at the battery, you may have 14.3 or something at the R/R brown voltage sense wire. Just an example.

I back-probbed the brown wire at the R/R connector & the voltage is less than at the battery by almost 1 volt.
What's causing the voltage drop? And how do I proceed? doh.

Use your wiring diagram, and look at the brown wire circuit. You will see that it starts back at the main fuse, before it is connected inside the ignition switch. I'd start there, at the main fuse, see if there is much of a volt drop. But Patton has a nice little diagram for checking each connection along the harness, and MFolks has a big list for cleaning Motorcycle Electrics, both are good reads.

Thanks. I was afraid you were going to say something like that... .... ugh.

It isn't hard to do at all. A least you know your charging system works, just a bit high on voltage. Once you clean up a few contacts, it'll be fine.

This generic diagram illustrates the places to check for undesired voltage drops between the battery and ignition coil.
However, it's for a points ignition with separate rectifier and regulator.



Good Fortune!