TOPIC:

The green wire is not ground.

The 1977 Kz650 uses an excited field alternator. The green wire is power to the field coil.

You can get a combination regulator/rectifier, but it is just a separate regulator and rectifier stuck together, so you can do fine with separate units.

The regulator is powered by the brown wire and regulates power to the green wire which powers the field coil. The black wire on the regulator is ground.

The aftermarket regulator shown in the OP's photos will need some sort of diagram to know what the wire colors mean. It appears to be a 1-phase shunting regulator for watercraft (Kawasaki Jet Ski JT750). It cannot be used on the 1977 Kz650, and I would not use it on any motorcycle. The wires look to be for light duty (watercraft don't need a lot of electrical power).

There should really only be 3 wires for the 1977 Kz650 regulator, as is seen in the factory diagram... 1 Brown, 1 Green, 1 Black.

Oregonmotorcycleparts.com has the regulator specifically for your bike. I would get one from them, they are not expensive.
www.oregonmotorcycleparts.com/vregulators.html
You want model VR3-KZ.

Thanks loudhvx. I’ve been contemplating SWest’s suggestion all day and I still had questions about having more wires than was being described.

I’ll have to chalk up the R/R unit I bought to a lesson learned in buying something before doing the research first.

Thank you for the link to that Oregon parts site. But you recommended the part number for the regulator which I still have and am assuming still works. I need the rectifier which on the other page is listed as R255a-KZ650 if I’m reading them all correctly.

The only question I have about the picture they show is that there is what looks like a green wire coming backwards out of the connector they have the three yellow stator wires going into. What exactly would this wire be for?

I assumed you wanted to replace both regulator and rectifier since you bought a combo unit. But if the mechanical regulator is working perfectly you can still use it with wet-cell lead-acid batteries. I prefer the more precise regulation you get with a solid-state regulator, especially if you are using a sealed-lead-acid (SLA) battery, (preferably absorbed-glass-matt AGM).

If all you need is a rectifier, the R255a-KZ650 should work. That green wire in the connector is probably meant to connect to the green wire on the regulator. It powers and controls the field coil in order to regulate the output power/voltage. They probably included it for convenience and to make it more plug-and-play.

You can also get a 3-phase rectifier on ebay usually for around $5.Several people have reported that they work fine. You would want a 50 amp rectifier or greater.

The AC side (input) of the rectifier is connected to the three yellows, and the DC side (output) should get a red wire for positive output and black for ground.