New Member with 1979 Z1300 A1

Thanks Globemaster... this is very useful information. Simple, regular testing at the battery and the fuse as part of a regular maintenance program could go a long way in preventing stator burnout.

Do you know what the acceptable voltage range is supposed to be for the sense circuit? The service manual isn't very clear on this... at least where I am looking. On page 234/235 in table K2 it says 15V. Is that accurate?

That 15 volts would be an approximation. The sense part of the regulator on all of this type of regulator normally turns the thyristors on at 14.7 volts.

I just had an aha moment and realized that I had installed one of these Shindengen MOSFET regulators on my 750 triple about 5 years ago. Worked a treat. The original rectifier/regulator had a leaky diode which constantly drained the battery. After installing the new unit, I did some testing and the output voltage was rock steady at 14.3 volts. No more problems. Best cure ever when rectifiers/regulators are no longer available. Really simple to install as well.

This is the stator I fitted 8 years ago which failed recently - oil pyrolysis evident on the stator coils and solder melted from the fly lead connections



This is the new stator that failed after one ride:



Thanks for the advice - I would also agree that it’s likely I have a sensing voltage issue caused by a poor connection in the main power circuit. I have checked the 9 way connector next to the fuse box (removing the individual male/female spade connectors) but it looks like the main power line (usually the brown wire) connects through the main switch, another connector and the ignition switch before getting back to the regulator. I cannot be completely certain, but the stator failures occurred when I rode with the headlight switched on (this is the European model with a light switch!) - this could easily have dropped the main power line voltage well below the battery voltage if there was a bad connection - thus triggering the stator failure.
This has all been really helpful so thanks again for the advice. It will be a pain to find the bad connection but I will spend an afternoon with my multi-meter measuring voltages at all the connectors with the lights on..

Neville,
After careful inspection of your detailed stator failure photos, I owe you a better analysis. There is no evidence of coil wires shorted to each other, or of windings shorted to ground. Both stators failed in the same manner, with the solder melted off of all 3 output leads. This indicates excessive current flow through each of the three stator winding phases.

Since the original stator lasted 8 years, and the replacement failed in the same manner after one ride, something obviously changed that caused the failure of both stators. My best guess is that something is wrong with the battery. A shorted battery cell/cells is almost like shorting the stator output to ground. If you have a standard lead/acid battery, maybe it got boiled dry and the stator put out maximum current trying to charge it.

You mentioned riding with the headlight on. This would have increased the current flow through the stator and added to the heat load caused by whatever went wrong.

One other thing that would have made the situation worse would have been a low oil level, since the stator is oil cooled.

The first thing to check is the battery. After that, make sure all grounds are clean and tight. Finally, check the oil level and keep it at maximum with clean oil.

globemaster wrote: Neville,
After careful inspection of your detailed stator failure photos, I owe you a better analysis. There is no evidence of coil wires shorted to each other, or of windings shorted to ground. Both stators failed in the same manner, with the solder melted off of all 3 output leads. This indicates excessive current flow through each of the three stator winding phases.

Since the original stator lasted 8 years, and the replacement failed in the same manner after one ride, something obviously changed that caused the failure of both stators. My best guess is that something is wrong with the battery. A shorted battery cell/cells is almost like shorting the stator output to ground. If you have a standard lead/acid battery, maybe it got boiled dry and the stator put out maximum current trying to charge it.

You mentioned riding with the headlight on. This would have increased the current flow through the stator and added to the heat load caused by whatever went wrong.

One other thing that would have made the situation worse would have been a low oil level, since the stator is oil cooled.

The first thing to check is the battery. After that, make sure all grounds are clean and tight. Finally, check the oil level and keep it at maximum with clean oil.

You've made some good points there Globemaster. Lead acid batteries fail when the porous lead plates start to flake off and the porous lead ends up in the bottom of the battery bridging acroos the positive and negative plates. That's why the battery manufacturers came out with the gel cell batteries. The gel acts as a shock absorber which helps the porous lead plates stay intact. For high vibration or inverted use they're the cat's ass. The down side to the gel cells is the slower charging/discharging rates and the older regulating systems don't like to work with them. If one was to upgrade to a MOFSET regulator and then add the gel cell it would be a good marriage of components.