Need a MODERN KZ rectifier

Nessism wrote: I see nothing special about that battery which would mandate changing the stock charging system.

BTW, your title and first post mentions a rectifier, not a combined regulator/rectifier unit. You gotta be specific if looking for "plug and play." What type of generator your bike has can be critical as well since KZ bikes used a few different types. Some have a field coil and others only two phases of AC output from the generator. Details matter when it comes to this sort of stuff.

For a permanent magnet three phase charging system the best R/R units are the SERIES type. I've posted so many times about this I sound like a broken record (to myself anyway). Find a real deal SH775 and install it. A simple swap that will improve your charging system to better than new.

I was hoping that I wouldnt need to upgrade and it sounds like i dont. I know lithium ION batteries can be problematic, but I didnt think lithium IRON phosphate batteries would be an issue. Glad to hear it.

So which is it, single or three phase?
Steve

SWest wrote: So which is it, single or three phase?
Steve

Im at work (Manhattan NYC) in the office. Though the bike is parked outside I havent the time to check. AND it seems like, with a lithium ION PHOSPHATE battery, I wont have to upgrade the rectifier

650Dude wrote:
Thanks! I think I want to go with a simple plug and play like the one in the link below, to avoid any issues:

www.dimecitycycles.com/vintage-cafe-race...-kawi-kz-10-304.html

Please be aware, none of the regulator/rectifier combos in this thread will be plug and play with the 77 Kz750B2 twin.

(Please make sure your bike is actually a 77 Kz750B2 twin and not a 78 Kz750B3 made in 1977. It makes a huge difference for the charging system.)

That dimecity listing is especially egregious. They need to go back to the drawing board on that listing. There is no way you can use the same unit on the bikes they list for fitment.

The 76-77 Kz750B twins use the most rare of all Kawasaki charging systems. First of all, it is 3-phase. (The dimecity unit is 1-phase.) Next, it uses what is called an excited-field alternator. That means it has a field coil and the regulation is done through controlling the field. But what makes the stock unit more unique than even the 77 650 or the 400's, is the way the field is controlled. Most Kz's with a field coil came with a mechanical regulator. The 76-77 750B were fancy in that they came with solid state regulators. Because of this, and more-so the fact that transistors from that era were more reliable when configured a certain way, the regulator controls the negative side of the field coil. The Kz's with mechanical regulators controlled the positive side of the field coil.

On the 76-77 750B, the field coil gets 12v from the brown wire whenever the bike is turned on. The green wire connects the field coil to the regulator. The green wire is the negative side of the field coil. The regulator regulates the field by controlling the current in the green wire.

You can re-wire the field coil to use a more universal field-coil regulator, but you don't have to.

Oregonmotorcycleparts makes one specific to the 76-77 750B model. I'm not aware of anyone else making one, but they probably exist. If you see other Kz's on the fitment list, then you know it's not plug-n-play for the 76-77 750B twin.

You need the VRREM3-KZ750T. Scroll through this page very slowly to see the listing.
oregonmotorcycleparts.com/Reg_rec_units.html

As you noted, you might not need a new reg/rec. The factory one on your bike was probably the best-performing charging system on a Kz, in terms of efficiency, overall output, and precision control of voltage. Any deficiencies would more likely be due to dirty wiring connections, which a new reg/rec can't fix, and may not be able to compensate for unless you reconfigure the wiring.

loudhvx wrote:

650Dude wrote:
Thanks! I think I want to go with a simple plug and play like the one in the link below, to avoid any issues:

www.dimecitycycles.com/vintage-cafe-race...-kawi-kz-10-304.html

Please be aware, none of the regulator/rectifier combos in this thread will be plug and play with the 77 Kz750B2 twin.

(Please make sure your bike is actually a 77 Kz750B2 twin and not a 78 Kz750B3 made in 1977. It makes a huge difference for the charging system.)

That dimecity listing is especially egregious. They need to go back to the drawing board on that listing. There is no way you can use the same unit on the bikes they list for fitment.

The 76-77 Kz750B twins use the most rare of all Kawasaki charging systems. First of all, it is 3-phase. (The dimecity unit is 1-phase.) Next, it uses what is called an excited-field alternator. That means it has a field coil and the regulation is done through controlling the field. But what makes the stock unit more unique than even the 77 650 or the 400's, is the way the field is controlled. Most Kz's with a field coil came with a mechanical regulator. The 76-77 750B were fancy in that they came with solid state regulators. Because of this, and more-so the fact that transistors from that era were more reliable when configured a certain way, the regulator controls the negative side of the field coil. The Kz's with mechanical regulators controlled the positive side of the field coil.

On the 76-77 750B, the field coil gets 12v from the brown wire whenever the bike is turned on. The green wire connects the field coil to the regulator. The green wire is the negative side of the field coil. The regulator regulates the field by controlling the current in the green wire.

You can re-wire the field coil to use a more universal field-coil regulator, but you don't have to.

Oregonmotorcycleparts makes one specific to the 76-77 750B model. I'm not aware of anyone else making one, but they probably exist. If you see other Kz's on the fitment list, then you know it's not plug-n-play for the 76-77 750B twin.

You need the VRREM3-KZ750T. Scroll through this page very slowly to see the listing.
oregonmotorcycleparts.com/Reg_rec_units.html

As you noted, you might not need a new reg/rec. The factory one on your bike was probably the best-performing charging system on a Kz, in terms of efficiency, overall output, and precision control of voltage. Any deficiencies would more likely be due to dirty wiring connections, which a new reg/rec can't fix, and may not be able to compensate for unless you reconfigure the wiring.

Thanks for all of this info. The OEM coil was bad so I swapped it out to this:

www.amazon.com/gp/product/B004O43Q9A/ref...04_s00?ie=UTF8&psc=1

Bike runs great now. Thanks for all the info you shared. Very valuable!

A field coil is not an ignition coil. Completely different things.