KZ-750 Charging

Iam restoring a 1976 750 and seem to be losing voltage slowly. Battery fully charged to 13.4 v . Drive around for 40 miles battery voltage drops to 13.1. Drive another 40 or so voltage drops to 12.7
Output of the three yellow wires are in the high 20's when run out to 4000 RPM. Main question - with the output desribed would a new stator help or does this sound like aging magnets - something I will have to live with.

Also I'm old and tend to putter in the country at 50MPH resulting in the Kawi not hitting 4000 RPM

P.S. After Many bikes this 750 is a fun bike to ride taking me back to a simplier time:cheer:

With the engine running you should have more than 14 volts at the battery at 1,100 rpm according to the book. Just a note, but never disconnect the voltage regulator with the key on, on these old girls or you can fry it.

These engine off test worked for me, maybe they'll help.

On the same 6 plug connector the armature leads are on there are also the field coil wires. A green one, and a brown one.

Resistance on the field coil between the green lead and brown lead should be between 2.7 and 3.4 ohm.. lower or higher and it is pooched.

Resistance between the chassis ground and any of the three armature leads should be non existent.. (modern world we live in I just used the continuity setting on my meter.. chuckle.) Any reading and there is a short in it. Pooched.

The resistance between each of the three armature (yellow wires) should be between 0.4 and 0.6 ohms.. otherwise it's pooched.

Rectifier test. quoted from the book.

"Disconnect the 4-pin connector on the electrical panel.
Using the R x 10 or R x 100 ohmmeter range, check the resistance in both directions between the white lead and each yellow lead, and between the black lead and each yellow lead. There is a total of 12 measurements. The resistance should be low in one direction and more than ten times as much in the other direction. If any two leads are low or high in both directions, the rectifier is defective and must be replaced."


Good luck, I hope this helps. Wow what a beauty old girl you got there.. very sweet! I think I'm jealous.

I wrote this for the bigger 4's, but I think a lot applies to your bike too:

Alternator Testing For the Older 4’s(Z1’s,Kz 900’s, Kz1000’s,Kz1100’s and GPz1100’s).

To check to see if the alternator is working you need to follow these simple steps:

1. Fully charge the battery as this will be the power source during this test.

2. Disconnect the Regulator/Rectifier at the plug that has the six wires in it.

3. Start the engine and let it warm to operating temperature.

4. If you're worried about overheating, position a large fan for cooling the engine.

5. After the engine has reached operating temperature, have a helper assist you, and using a multi-meter, read the output at the three yellow wires (or the alternator output wires)at the disconnected connector.

6. Raise the engine speed to 4000 rpm, and see what the three YELLOW wire combinations(or any alternator output wires) are(1-3, 2-3 & 1-2). The output will be around 50 Volts A.C.(Alternating Current). BE CAREFUL, AS THERE IS A SHOCK HAZARD HERE!!


7. If any of the combinations are low or non-existent, the stator(wire windings) are bad and must be replaced.
Some of the older Z1’s and KZ900’s were phase sensitive, so check the wire colors carefully.

8. Using an OHMETER, Check the three wire combinations again, looking for a reading of 0.36 - 0.54 OHMS. If the readings are above or below, the stator may be bad and need replacement. Also check from any of the three YELLOW wires to ground, this will show if arcing took place.

9. Before ordering a new stator, check the connections from the stator as there are electrical "Bullet" connectors that may be damaged or dirty.
Inspect the wiring for signs of shorting or overheating too. www.z1enterprises.com sells replacement rubber grommets for the alternator output wiring, they get hard and could leak oil after a while.

10. Check the wiring coming out of the grommet as there have been situations where the wires were damaged causing a short(I.E. twisted together with insulation damage).

11. The sprocket cover will have to be removed to access the electrical connectors coming from the alternator, the left foot peg assembly and shifting lever will have to come off also.



Alternator Stator Replacement On the Older 4’s
Source for replacement Stators

A. www.electrosport.com (They have a trouble shooting page)
B. www.customrewind.com
C. www.rmstator.com
D. www.ricksmotorsportselectrics.com
E. www.regulatorrectifier.com

1. If by testing either by checking the output voltage from the stator or by using and ohmmeter for resistance and the stator is determined to be bad, replacing the stator is not a difficult job.

2. The motorcycle owner should have on hand a replacement alternator gasket as it will tear on removal and leak if reused.

3. Put the bike on the center stand if possible and lean it to the right to minimize the oil volume that could come out when the alternator cover is removed.

4. Have selection of Metric wrenches and sockets along with Metric Allen keys to be able to accomplish this repair. ¼" and 3/8" ratchets and extensions may be needed along with Allen bits.

5. Remove the gear shift lever, the sprocket cover and possibly the left foot peg assembly.


6. A catch pan for what little oil will be lost should be positioned under the alternator on the left side. Newspapers will soak up any oil lost or some kitty litter will do as an absorbent.

7. Remove the alternator cover fasteners, some bikes use a socket head cap screw(Allen type) and others use the Phillips head type, the #3 screwdriver bit fits best for those. Use a small dish or can to collect the removed fasteners from the parts to prevent loss/damage.

8. The alternator stator is secured to the inside of the cover usually with three Allen headed bolts, Some bikes may have Torx style fasteners, Remove them and disconnect the three yellow wires that have bullet connectors on them from the bundled wires inside the sprocket cover.

9. If your bike has some color other than yellow for the alternator output wires, make note of what goes where as the older Kawasaki’s were phase sensitive in regard to the regulator/rectifiers.

10. When installing the replacement stator, clock or position the output wires and grommet so they fit into the small port under the alternator cover without being pinched or damaged.

11. Tighten the three Allen or Torx fasteners, securing the replacement stator to the cover. I like using the BLUE Loctite # 242 for hardware that can be removed with hand tools.

12. Remove the old gasket from the mating surfaces of the alternator cover and engine case by scraping with a piece of sharpened plastic like Lexan or Plexi-glass as these will not gouge the soft Aluminum Cases. Avoid using a metal gasket scraper for this.

13. Position the alternator cover, checking for pinched wiring and install the fasteners with a little silver anti-seize on the threads, tightening to the correct torque.

14. Connect up the output wires to the mating female bullet connectors and while you’re in there, check the routing of the wire bundle that runs through there.

15. Inspect for signs of heat damage to the wire insulation and vibration damage too.

16. The side stand switch, neutral switch, and oil pressure switch wiring are all bundled with the alternator output wiring running above and behind the engine output sprocket. This bundle runs in a channel as it goes up toward the various electrical connections.

17. The regulator/rectifier plug on the 80’s bikes usually has six wires in it:

A. One (1)WHITE with RED stripe, this is the bikes main power wire usually 12 gauge in size.

B. One(1) smaller Brown wire, probably 18 gauge or so, the voltage sense wire for the regulator/rectifier, helps keeping it from overcharging the battery.

C. One(1) BLACK with YELLOW stripe wire, part of the ground circuits, maybe 16 gauge in size.

D. Three(3) YELLOW wires, maybe 14 gauge in size, the alternator output wires going to the regulator/rectifier which converts the Alternating Current(A.C.) to Direct Current(D.C.) using rectification, producing the power to run the motorcycle and charge the battery.

18. Reinstall the sprocket cover, again checking for pinched wires before tightening. Install the shifter on it’s splined shaft checking for proper location, and the left side foot peg assembly.

19. Except for the minor oil spill and reluctant fasteners, it’s not a very difficult job to do.

DBINWI wrote:

...Output of the three yellow wires are in the high 20's when run out to 4000 RPM. Main question - with the output described would a new stator help or does this sound like aging magnets - something I will have to live with....

What are factory specs for yellow wire outputs?

Good Fortune!

DBINWI wrote:

...losing voltage slowly. Battery fully charged to 13.4 v . Drive around for 40 miles battery voltage drops to 13.1. Drive another 40 or so voltage drops to 12.7....

Perhaps just a failing battery ---

Fluids to proper level?

Specific gravity check?

Load test?

Or poor cable connections ---

Cable terminals clean and snug?

Good ground connection where negative battery cable attaches to engine?

Good Fortune!

Capt America wrote:

... Just a note, but never disconnect the voltage regulator with the key on, on these old girls or you can fry it.
...

Never heard that before. Why would that fry the regulator?

loudhvx wrote:

Capt America wrote:

... Just a note, but never disconnect the voltage regulator with the key on, on these old girls or you can fry it.
...

Never heard that before. Why would that fry the regulator?

Oh I dunno, I'm no electrician or electronics guru.. chuckle.. it's just been highlighted in every book Haynes/Factory Kawasaki as a warning so I thought I pass it on to you since your digging through your electronics trying to find your charging problem. This is quoted right from the factory book.

CAUTION If the regulator connector is disconnected with the ignition switch on, the regulator may be damaged.

On that type of charging system, disconnecting the regulator would only prevent damage to the regulator, and rest of the system (even when running).

Is it possible they said not to disconnect the regulator while it is running on the old Z1/KZ900 bikes? On those bikes, disconnecting the regulator and running the bikes can fry the whole bike. That would also apply to the 750's that had permanent magnet alternators and seperate regulators and rectifiers, if they exist. But that's not the type he has on a 76 750 B1, at least not according to Kawasaki.com.

Thanks for the responses. I'll try some of the ideas sent my way.
One more question--- How much oil is lurking inside the alternator and starter cover? When I opened mine up I lost about 3/4 Qt with bike on the side stand
Can excessive oil cause problems?

That should be about normal, especially when on side stand. On the KZ's, the big bikes, and the twins have a little oil to the alternator. The 550, 650, and 750-4 have seals there so no oil.

Obviously, you probably want to use the center stand if you have one, just to save some oil.

loudhvx wrote:

On that type of charging system, disconnecting the regulator would only prevent damage to the regulator, and rest of the system (even when running).

Is it possible they said not to disconnect the regulator while it is running on the old Z1/KZ900 bikes? On those bikes, disconnecting the regulator and running the bikes can fry the whole bike. That would also apply to the 750's that had permanent magnet alternators and seperate regulators and rectifiers, if they exist. But that's not the type he has on a 76 750 B1, at least not according to Kawasaki.com.

Not to be argumentative, but that quote is right from the Kawasaki B1/B2 Manual. That bike won't have the permanent magnet yet, it'll be the old stator, field coil, regulator, rectifier. Like I'm now using from a 77.

Capt America wrote:

loudhvx wrote:

On that type of charging system, disconnecting the regulator would only prevent damage to the regulator, and rest of the system (even when running).

Is it possible they said not to disconnect the regulator while it is running on the old Z1/KZ900 bikes? On those bikes, disconnecting the regulator and running the bikes can fry the whole bike. That would also apply to the 750's that had permanent magnet alternators and seperate regulators and rectifiers, if they exist. But that's not the type he has on a 76 750 B1, at least not according to Kawasaki.com.

Not to be argumentative, but that quote is right from the Kawasaki B1/B2 Manual. That bike won't have the permanent magnet yet, it'll be the old stator, field coil, regulator, rectifier. Like I'm now using from a 77.

Not taken as argumentative at all. You are just quoting the book. That's how we get to find errors in manuals (in case you haven't followed the other charging saga recently ).

Since the B1 has the field-coil type alternator, I can't imagine why removing the regulator could do any damage. Essentially you are just removing all power from the alternator, and the regulator is unconnected.

I suspect they threw the warning in to copy what was in the KZ900 manuals. The KZ900 is a totally different system, so it is importatn on that bike to keep the regulator functioning when the bike is running. I also suspect they misinterpreted the warning to be anytime the bike is turned on, when in fact, the warning should be for anytime the crankshaft is turning.