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New Member with 1979 Z1300 A1 4 years 1 month ago #14656

  • Neville
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Had this bike since 1985 - and following the website since it was formed - outstanding!. Completed all the recommendations including getting a manual, cam chain tensioner, petcock, water pump seal (tricky!), ultrasonic carb cleaning and numerous other improvements including replacing all the inlet valve stem seals. Have also replaced all the brake discs and overhauled the callipers. Latest issue has been generator/regulator. First stator lasted until 2008, second until recently and third for one ride only. I have a new regulator which passes all the diode tests. Checked all the connections and replaced a number but suspicion is now on the fuel solenoid valve - I took this out of the fuel circuit 20 years ago but it connects to one of the stator leads? Anyone else had this problem?

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New Member with 1979 Z1300 A1 4 years 1 month ago #14660

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A stator fails either from an overload, a short, or an open circuit. Can you determine what is actually wrong with the failed stators? Are the windings burning up?

A bad connection at the electrical plug between the stator and voltage regulator can overload the stator causing it to overheat and burn the windings. This is a common problem and the solution is to remove the electrical connector, solder the wires together and insulate them with heat shrink.

The other common problem is the metal strain relief for the stator wires cutting through the insulation and creating a short.

Maybe the latest stators have manufacturing defects.

Removing the fuel solenoid valve should have zero effect on the stator. If anything, it reduces the electrical load.

One remote possibility is that the stator is the wider 1980 version. I'm uncertain if the cover would even bolt up with it in place, but if it did, the stator would rub on the flywheel.

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New Member with 1979 Z1300 A1 4 years 1 month ago #14664

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Thanks for the reply - all of the failed stators show signs of overheating - the last one had some soldered connections between the windings and the fly leads on the stator body itself which had melted. I have measured and checked the dimensions and its the right one for the A1 - don't think the deeper units would allow the case to bolt on anyway. The last two stators had the wire guide bracket which all seemed OK (no sharp edges) but the latest one I have purchased (from Electrex World) has the right dimensions, looks better quality but has no guide bracket or threaded holes in the central core that I could fit one of my old brackets into. I have replaced all of the Regulator connectors (7 off) with single soldered insulated spade connectors but I am suspicious of the main connector that couples to the fuse box and battery - I will overhaul this next.
Thanks again for the reply - great website and support

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New Member with 1979 Z1300 A1 4 years 1 month ago #14670

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Thanks for the information about the stators overheating. First, four basics must be observed.

1. The stator cover must be perfectly round. An out of round cover will cause the stator to burn up. Any dents or gouges in the cover will compromise the cover concentricity. The only way to accurately check the cover for roundness is with a micrometer.

2. The stator is partially oil cooled. Dirty oil will not cool as effectively as clean oil. A low oil level will also prevent proper cooling of the stator. Change the oil and filter at the proper intervals and maintain the correct oil level.

3. The cooling of the stator is also dependent on the engine temperature. The higher the engine temperature, the harder it is for the stator to dissipate heat. Make sure the engine cooling system is operating at maximum efficiency.

4. The stator itself must be of high quality. This is primarily true of the stator winding insulation. If it fails, the windings short and overheat the stator.

The 1979 A1's were prone to stator overheating for 2 reasons:

A. The oil cooling of the stator is by oil splashing onto it. The 1980 models had an oil feed to the stator to address this problem.

B. The voltage regulators tended to overcharge the battery. To regulate the voltage, the regulator grounds the stator output. This in effect shorts the stator current back into the stator. The stator must then dissipate this power as heat. A better voltage regulator will help prevent this. Some knowledgeable people use the voltage regulator from a Yamaha Venture Royal. The ultimate cure is probably a Shindegen MOSFET voltage regulator. It will turn off voltage flow instead of shunting it to ground.

For the voltage regulator to function properly, the sense voltage must be correct. Any dirty, corroded, or bad connection of the sense wire (brown wire from the regulator) will cause a voltage drop. Hint: The sense wire obtains voltage from a 10 amp fuse in the fuse box. The fuse box connects to the wire loom with a 9 pin connector. Any bad connection of the brown sense wire in these locations will lower the sense voltage. Any bad connection between the battery and the 10 amp fuse input will also drop the sense voltage. Battery voltage to the 10 amp fuse runs through the main switch and the ignition switch. Any bad connections inside or at the connectors of either switch will lower the voltage. The lower voltage will cause the regulator to overcharge the battery, and overheat the stator. All of the connections supplying sense wire voltage must be clean and tight. A quick check would be to test the voltage at the battery. Then test the voltage at the 10 amp fuse that feeds the sense wire. If the voltage at the fuse is significantly lower than the battery voltage, that is part of the problem - maybe THE problem.

A common modification to help prevent battery overcharging is adding a 20 amp, single pole relay to the voltage regulator sense circuit. The brown sense wire is cut. The end from the voltage regulator connects to one side of the relay contact. A wire is added from the other side of the contact and goes directly to the battery positive terminal. The sense wire that went to the regulator is connected to one of the relay coil terminals. A wire is added from the other coil terminal to ground.
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Last edit: by globemaster. Reason: corrected typo

New Member with 1979 Z1300 A1 4 years 1 month ago #14671

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globemaster wrote: Thanks for the information about the stators overheating. First, four basics must be observed.

1. The stator cover must be perfectly round. An out of round cover will cause the stator to burn up. Any dents or gouges in the cover will compromise the cover concentricity. The only way to accurately check the cover for roundness is with a micrometer.

2. The stator is partially oil cooled. Dirty oil will not cool as effectively as clean oil. A low oil level will also prevent proper cooling of the stator. Change the oil and filter at the proper intervals and maintain the correct oil level.

3. The cooling of the stator is also dependent on the engine temperature. The higher the engine temperature, the harder it is for the stator to dissipate heat. Make sure the engine cooling system is operating at maximum efficiency.

4. The stator itself must be of high quality. This is primarily true of the stator winding insulation. If it fails, the windings short and overheat the stator.

The 1979 A1's were prone to stator overheating for 2 reasons:

A. The oil cooling of the stator is by oil splashing onto it. The 1980 models had an oil feed to the stator to address this problem.

B. The voltage regulators tended to overcharge the battery. To regulate the voltage, the regulator grounds the stator output. This in effect shorts the stator current back into the stator. The stator must then dissipate this power as heat. A better voltage regulator will help prevent this. Some knowledgeable people use the voltage regulator from a Yamaha Venture Royal. The ultimate cure is probably a Shindegen MOSFET voltage regulator. It will turn off voltage flow instead of shunting it to ground.

For the voltage regulator to function properly, the sense voltage must be correct. Any dirty, corroded, or bad connection of the sense wire (brown wire from the regulator) will cause a voltage drop. Hint: The sense wire obtains voltage from a 10 amp fuse in the fuse box. The fuse box connects to the wire loom with a 9 pin connector. Any bad connection of the brown sense wire in these locations will lower the sense voltage. Any bad connection between the battery and the 10 amp fuse input will also drop the sense voltage. Battery voltage to the 10 amp fuse runs through the main switch and the ignition switch. Any bad connections inside or at the connectors of either switch will lower the voltage. The lower voltage will cause the regulator to overcharge the battery, and overheat the stator. All of the connections supplying sense wire voltage must be clean and tight. A quick check would be to test the voltage at the battery. Then test the voltage at the 10 amp fuse that feeds the sense wire. If the voltage at the fuse is significantly lower than the battery voltage, that is part of the problem - maybe THE problem.

A common modification to help prevent battery overcharging is adding a 20 amp, single pole relay to the voltage regulator sense circuit. The brown sense wire is cut. The end from the voltage regulator connects to one side of the relay contact. A wire is added from the other side of the contact and goes directly to the battery positive terminal. The sense wire that went to the regulator is connected to one of the relay coil terminal. A wire is added from the other coil terminal to ground.


Some REALLY good info there Globemaster !! Thank you for that. A logical explanation of the issue with a few samples of how to overcome the issues, along with a sample of common available technology that an average person could use and then the MOFSET cure for those that understand this technology. REALLY GOOD INFO and well written.

I plan on cutting/pasting this into a note section in the electrical section of my manual for future consideration..
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New Member with 1979 Z1300 A1 4 years 1 month ago #14672

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Kawboy,
Thank you for such positive comments. The KZ1300/ZN1300's were far ahead of their time. Every one of them ever built deserves to still be on the road. It is my pleasure if I can contribute in a small way to help owners keep them alive.

In my humble opinion, the relay modification to prevent battery overcharging circumvents the cause, but does not cure it. The real cause is voltage drops in the regulator sense circuit. This is probably from poor internal contacts in the main and/or ignition switches. If that is the case, then other items receiving voltage via the main and ignition switches will also receive subpar voltage.

Guys like you and Scotch are the stars of this forum. Thanks to both of you for all the help you have given your fellow 1300 enthusiasts.
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