16.6 volts???

I have a 1977 KZ650B1 that seems to love putting out the volts. The bike was a hack job when i bought it but i have carefully rebuilt the machine back to running order and used professional mechanics where my skills were a bit short.

Now, when I put my meter on the battery leads at idle (1000 rpm) I am reading 12.8 volts or so. By the time I rev to 3000 rmps I am soaring over 15 volts. I've seen readings as high as 16 volts!

Now - the ENTIRE charging system (battery/regulator/recitifer) are NEW. I've driven the thing for almost 3,000 miles without losing a bulb or the battery cooking. All the wires are routed/attached/grouned as per the manual. So what is going on? Where do I even start looking for a fault? And if I'm actually putting out all that power why haven't I toasted something yet?

Using a digital or analog meter? some digital meter's are sensitive to the magnetic field produced by the alternator's rotor. If possible, re-check the readings with an analog meter(the kind with the needle pointer and multiple scales.

Hmmm ... interseting point. Yes, it is a digital meter. I suppose i could find a different meter and re-test. As I said it runs/drives fine (although i do notice the headlight is a little dim at idle than when running at speed).

I suspect the digital meter is at fault, over voltages like this will quickly blow lights and over charge the battery and related systems.

If the meter is confirmed ok by a second meter, there are two likely causes.

One is simply the regulator is faulty.

The second (and more likely if the wiring is original) is that you are losing voltage on the brown wire at the regulator. That is the wire the regulator uses to determine how high to let the voltage climb. Dirty connections at the fuses, ignition switch, wires, connectors etc, can reduce the voltage on that brown wire. The regulator then compensates by increasing the voltage to the battery.

The test is to use the battery negative terminal as the ground test point, then compare the voltage on the battery + against the voltage on the brown regulator wire while the bike is revving. This will take alligator clips or two people. The brown wire should be less than 1-volt different from the battery. It is lower than the battery by more than 1 volt, try cleaning the fuse holders first.