Alternator / Rectifier

Been browsing the site for a few weeks to get a new to me bike going.
It's going now so thanks to the site.
Battery however is not charging so it's stuck connected to a trickle charger.
I've tested the Alt and get 40+ volts from any combo of yellow wires at idle.
On the resistance test I am getting .9 from all.
If the output is good does the high resistance matter?
On the rectifier I have a short between one of the yellow wires and the red + wire.
I've disconnected the alt wire going to that lead on the Rect. and it seems to be charging some.
Will it hurt the Alt if I take it for a spin around the block w/ one lead disconnected?
Any cheap source for a new rectifier, or can they be rebuilt? (it's under the batt box so I haven't seen it yet)
THANKS!

Loudhvx has a description of how to build your own reg/rec on his site I believe.

They are commonly available used, and I think Ricks and Electrosport sell new replacements.

couldn't find his site, would be curious on the DIY even though they seem to be had cheap on ebay.

Does sound like I can atleast take her for a spin around the block atleast (finally). Just need it to dry up a bit outside

from another post

loudhvx wrote:
when the stator wires are open (not connected), there is no electrical current, just voltage. It should not hurt anything.

Yes, I agree that it should not hurt anything to have one of the yellow rectifier wires unplugged.

I built a rectifier from plans. It was a worthy project, and it taught me a lot about the inner workings of the bike.

Radio Shack supplied the parts.

www.geocities.com/loudgpz/

In his case, he needs the regulator and rectifier. I have plans for them seperately,
Regulator
Rectifier ,

but it's cheaper to buy them as a single combo-unit on ebay, as long as the one he gets is good.

Very nice plans, good work, but the reg/rec is probably over my head.
Well, I got to take it for a ride today... That was good.
Came home and pulled it apart. The reg/rec unit in it is not what appears in the manual. Guess it's off something else.
The rec/reg has only 3 yellow going into the harness, red going to starter relay, and black grounded to frame.
The 6pin connector (only 5wires) on the harness has nothing connected to the Brown or Black/yellow.
Neutral indicator & oil light work correctly (brown)
Cannot confirm anything on the Black/yellow wire works...
Turn signals work but only w/ the Man/Auto selector switch in the middle. Not sure what that switch is, so maybe thats proper function.
Would all bulbs accessories work without the 2 wires terminating correctly?
Is it safe to put a factory 6wire reg/rec in without going over the entire harness looking for other modifications the previous owner did, specifically the Br and Bk/Y wires?

In the above green ribbon, point to KZ Information and click on Filebase in the drop-down menu. Then click on 1981. Scroll down to see separate listings for KZ750-H2 and E2. Click either one and be able to download its wiring diagram. Maybe one of the wiring diagrams will be helpful.

I viewed both diagrams and will try to include the links here in this post. But if these links don't work, just navigate from the green ribbon.

Good Luck!

1981 KZ750-H2 Wiring Diagram

1981 KZ750-E2 Wiring Diagram

The original reg/rec worked as follows:
3-yellows: 3-phase AC from stator to reg/rec.
Red : 12~14vDC output from reg/rec to battery via starter solenoid.
Black/Yellow : Ground. It connects to battery via harness
Brown: Switched battery voltage from ignition switch to reg/rec. This is what the stock reg/rec used to measure the system voltage in order to know whether to increase or decrease output. It is a switched wire so as to not drain the battery when the bike is off.

Your present reg/rec is different. It does not need that seperate brown line to detect voltage. It detects the voltage at the output red wire. The black wire to frame ground may be of concern. The frame is not always a good ground to the battery. You should run an additional wire from that frame ground point back to the black/yellow on the reg/rec connector to have redundant grounds.

Sounds like there's no harm with them currently not hooked up or if I were to replace the rec/reg with at factory piece. Thank You

Thanks also for the links, I do have the factory manual.

Brown: Switched battery voltage from ignition switch to reg/rec. This is what the stock reg/rec used to measure the system voltage in order to know whether to increase or decrease output. It is a switched wire so as to not drain the battery when the bike is off.

Got a used Reg/Rec and it's charging, Actually over charging.
It appears the brown wire is about 1.5v less then batt volts.
Is there a common fix for this?
Maybe clean the contacts under the ignition key?
Looks like this is my last obsticle before taking a long ride
THANKS

enormiss wrote:

Brown: Switched battery voltage from ignition switch to reg/rec. This is what the stock reg/rec used to measure the system voltage in order to know whether to increase or decrease output. It is a switched wire so as to not drain the battery when the bike is off.

Got a used Reg/Rec and it's charging, Actually over charging.
It appears the brown wire is about 1.5v less then batt volts.
Is there a common fix for this?
Maybe clean the contacts under the ignition key?
Looks like this is my last obsticle before taking a long ride
THANKS

That is a very common problem. Dirty fuse holders is often the cause. Next likely would be bad contacts at the ignition switch. Next would be bad connections at the various connectors in the circuit.

You should also verify all the grounds involved read zero volts (relative to the battery negative).