15.5 V. @ 3,000 RPM

Just changed the alternator seal on my KZ900. Had to cut the wires and solder and shrink wrap them. Checked voltage afterwards to make sure alt was working. 12.8 v static, 3 K rpm..... slowly climbs to 15.5 V. Seems too high. Time for a new RR?

The original voltage regulator on my 1977 KZ650 is adjustable. Maybe yours is too? Ed

Do you have a way to monitor voltage while riding? A constant 15.5V may harm the battery and shorten bulb life. If it just hits that for short periods of time, no harm.

ckahleer wrote: Do you have a way to monitor voltage while riding? A constant 15.5V may harm the battery and shorten bulb life. If it just hits that for short periods of time, no harm.

I just ordered a voltmeter so I can do just that. Probably a good idea to have a voltmeter on all of these old bikes. Charging system goes out when you're a couple hundred miles away, you have no way of knowing until the battery runs down then you're screwed. I've let it run at 3 K while I monitored it. The voltage regulator catches it at 15.5 and drops it to 15, then cycles back and forth.

To high, regulator not working.

73z1 wrote: To high, regulator not working.

Maybe / maybe not. If it is like the 1977 KZ650 and is adjustable it just needs to be adjusted down a little bit. That's all that the one on my KZ650 needed, and I found it to be very simple to do. It cost me less than 10 minutes to do and zero cash outlay. The KZ650-B1 manual gives specific instructions (see below), maybe his manual does too if his is adjustable. Ed

Interesting Ed. Does anyone know if the regulator on the KZ900 is adjustable like the KZ650?

Your problem could be resistance in connectors or grounds. A voltage regulator has to sense voltage accurately in order to correctly regulate it.

The 900 uses an electronic regulator. The regulator Ed is talking about is a mechanical regulator for a totally different type of alternator.

As ckahleer said, you have to check the sense line which is the brown wire of the regulator and make sure that brown wire has voltage on it within a volt of the battery voltage.

It's easy to check. With the bike running, put the red meter lead on the battery positive, and the black meter lead on the brown wire at the regulator. If it's more than a volt or so, a new regulator might not fix the problem. The problem is voltage loss in your system and the regulator is compensating by increasing output to the battery.

The manual probably has detailed tests for the charging system.