BS350 Rectifier & Regulator replacement

[OldSwartout]

Electronic rectifier/regulator for Bridgestone 350:

My 350 GTR dried out the AGM battery that was only 8 months old.  Investigating the charging system revealed the regulator was no longer functioning. There was a buildup of rust, filings and other debris between the magnet and the arm that moves the contacts, preventing the arm from moving and therefore keeping it from regulating. The debris easily blew out with air, but rather than risk another battery, an electronic system seemed a better choice.

[OldSwartout]

My brother remembered that some of the Kawasaki’s that he had in the barn used a three wire alternator similar to the Bridgestone.  A little investigation showed that some KZ550 & KZ650s used a regulator/rectifier with the correct number of connections. These are available used from many places.  They can be found on Ebay for around $25.

You need one that has a connector like the one shown; six position connector with five connections. Three of these will be yellow wires for alternator connections, a black/yellow for ground, a brown for regulation and a separate white/red wire for battery positive.  These were used on Kawasaki Kz650 models F2, H1, H2, D4 and some KZ550s from 81 through 83.

[OldSwartout]

I was lucky enough to get the mating connector, but of course, if not available, wires can be cut and connected using bullet connectors or others of your choice.

1.   Remove the current selenium rectifier from under the seat and the mechanical regulator from under the tank.

2.   Mount the regulator/rectifier in place of the original rectifier. I mounted mine directly to the top of the battery box, putting the screw heads inside the box so the ends wouldn’t interfere with the battery.

3.   Alternator connections – connect the yellow, light green and brown wires from the alternator to the three yellow wires on the regulator/rectifier.  The brown wire from the alternator currently connects to a wire going to the ignition switch and returns as a white wire to the rectifier.  This part of the circuit is now unnecessary.  You’ll be hooking all three wires directly to the regulator.  No need to switch 1/3 of the alternator on and off with the lights.

4.   Connect the black/yellow wire from the Kawasaki regulator/rectifier to ground.

5.   Connect the white/red wire from the Kawasaki regulator/rectifier to the battery positive (original red wire on the bike).

6.   Connect the brown wire from the Kawasaki regulator/rectifier to the blue wire circuit on the bike.  This brown wire is the regulator lead.  I put some blue heat shrink tubing on mine to help identify it if disconnected sometime.

Here’s a modified schematic:

[OldSwartout]

A photo of my installation with the regulator/rectifier mounted on top of the battery box. (Ignore the horn bracket – my horn was once mounted here.)
 

[slawsonb]

Excellent transplant surgery, Karl. This will make a much better/less problematic system for our BS's. Nice job documenting as well. Thanks.
...bert

[OldSwartout]

I think this would work on a 175/200 also, but won't get a chance to try it for some time.

My 350 now has electronic ignition, H4 headlight and more modern regulator/rectifier.  Maybe someday a disc brake and fuel injection...

[BRT-GTR]

     Great job, Karl, with idiot proof instructions, just what we need.   . I'll be fitting one of these to my everyday runner. Think you will find the points and condensers from a Z650 and similar Kawasakis will also fit the GTR.
       Brian.