Battery not being charged, replace regulator – KZ550

Filed under: KZ550

This post is part of my KZ550 restoration project.

I bought my KZ550 from my father-in-law, sadly it wouldn’t start! I had my friend Paul come to collect it, but before we moved it we tried starting it some more. The battery was flat, so we hooked up some jump leads from his truck to the bike’s battery.

That instant, the bike started smoking. I ran away in fear of a wild gasoline explosion, but luckily Paul’s quick reactions found the culprit and disconnected it. From the positive terminal on the battery, following the cable down the side of the bike to where it splits into two, one of the two connects to the regulator.

It took me a while to realise what the problem was, but the symptoms were as follows:

Riding the bike for a minute would be followed with the engine stalling. There was no stutter, just complete death!
After the bike had shut down, it would start right back up if I turned the starter.
The battery seemed to flatten quickly.

On the KZ550, the regulator and rectifier is built into one unit. This unit controls the voltage coming from the bike’s stator (a series of magnets that create voltage), without this unit the battery won’t be charged and the bike will be forever running on battery power.

After investigating, I found that the wire connecting from the regulator to the positive side of the circuit (leading back to the battery) was shortcircuiting against the regulator’s casing. Because the unit is sealed, my only option was to replace it.

After a long tedious search on eBay, I found a replacement unit. The difficult part was matching up the connectors – as some have four pins, some have five, and they all come in different shapes and sizes! Bear in mind that when you order a regulator, more important than matching the socket is making sure the number of wires and their colours are the same as the original on your bike.

When the regulator arrived, it became quickly apparent that it wasn’t what I ordered! It was for a different KZ, I ended up having to solder the connector from the old regulator to the new regulator. This was simple:

Cut the wires on the old regulator as close the regulator as you can.
Cut the wires on the new regulator as close to the connector as you can.
If any of the wires look damaged, cut off the damaged part.
Strip and tie each wire together according to their colours.
The yellow wires can be connected in any order, as these come directly from the stator which produces AC power.
Solder the wires to enforce the connection.
Wrap the wires in wire tape.

Once repaired, I added the regulator back to the bike and promptly started the bike. To make sure it’s providing power, follow these instructions:

Start your bike and warm up the engine.
Disconnect the negative connector on the battery.
If the regulator is providing power, the bike should continue to run.
Note: You may notice that the headlight flickers and that revving the bike results in rough running while the battery is disconnected. This is normal behaviour when your battery is disconnected. But there should be enough power to keep the bike running at idle.

And that’s it! Let me know about your experiences.

Posted by Steve on April 6th, 2009

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