Stator Failure '79/'80A

I replaced my stator 3 yrs ago (along with a MOSPHET regulator).
I've now just replaced this one ! All 3 phases shorted to ground and winding ties (a type of cord or string) that secure the 3 output leads), burnt to a crisp and in pieces. This is stator #6
I've been "smashing eggs" the past two weeks trying to understand why my stators are baking like 'tators in the Kawasaki Easy Bake Oven. I've come to some conclusions.
* The only notable auxiliary load on my electrical system is 55W driving light. Instrument cluster lighting is all LED as are my two front signals, brake and tail light.
It's my understanding that the '80B's and up had the alt. cover cast to supply an oil-spray to cool the stator. The '79 and '80A's did not have this oil spray feature. That's not to say there's no oil in the'79/ '80A covers. There is....and a lot more then one might suspect. The oil comes from the crankshaft end bearing. This oil is returned to the oil-pan through a port in the crankcase, adjacent to the bottom of the cover. I will further surmise that Kaw. made an effort (?) to cool the non-sprayed stators by utilizing air circulation within the cover. It was likely Kawasaki's assumption that the oil being discharged out of the end bearing plus some air movement would be adequate to cool the Stator. Clearly it's not. The subsequent change to an actual oil-jet spray substantiates this.
Note the two covers. '79/80A vs. the later oil-spray version.


The oil nozzle in the later versions can be seen in the inside of the stator pedestal. Note on the '79/80A, the "notch" in the pedestal. The "notch" is not present on the oil-spray version. I believe that this notch was intended to provide a path for air flow into the center of the stator where the spinning rotor centrifugally discharges this air within the cover. The rotor acts as a rudimentary squirrel cage fan. How much oil is scavenged and distributed along with this air is unknown but clearly not adequate to sufficiently cool the windings. The problem with this design is there is no replacement/supplemental air to aid in cooling. The air within the cover just gets hotter and hotter and eventually the insulative coating on the windings fails from heat break-down and that's the end of the stator.
For the past two weeks I've broken a few eggs trying to figure out how to get a continuous supply of cooler air into my cover. So far without success.
I suspect that there are more stator failures on the '79/'80'S being blamed on the OEM voltage regulators, then may be fair. Always a controversial topic: Which failed first? Did the V/R fail and take out the stator of did the stator fail and take out the V/R?
My personal opinion based on my somewhat extensive experience and continued bad luck is the '79/'80A Stators fail first, in most cases.
I'm now approaching the "cooling" issue from another angle and if I find what I believe to be a viable solution, I'll come back to the topic.

HI Scotch,

Interesting one this.
I have owned one or two 1300's which have melted stators like this too, and just assumed normal life expectancy, yet a friend and owner of mine who had two 1300's did not need to change them for nearly 40 years and 40k miles.
One of the most common issues related to the stator failing was the 3 way block connector from it positioned behind the RH side panel.
The spade connectors on these often corroded, which then lead to it burning or melting and eventually the stator failing if not rectified in time.

I have fitted one of these very low cost and very effective devices to my own Z1300 as its both a Digital Clock and very accurate Volt Meter, which lets you keep an eye on how the charging system is doing as you ride. Takes minutes to fit and is a perfect fit when stuck to the rear face of your front brake master cyinder.
This will not stop the stator melting, but it wil at least provide a warning when it starts to go.!

EBAY 223680276624

Pete F
UK

Years ago I removed the Alt. Lead plug and solder these connections. Hasn't seemed to do any good. The connecting plugs (terminals) found on the MOSPHET V/R's are large and robust so no concerns about these. Again, I'm convinced that the lack of cooling is destroying the stators. There's a solution - I just need to find it !

Forgot to mention: I changed out the 16g stator leads to 14g with much better means of attachment, then they typically come with. I doubt this in itself will have any advantage in making the stator last longer but, "Bigger is Better" I thought, in this situation.

I have yet to own a Japanese motorcycle where the 3 yellow wire alternator connector doesn't burn up - even on old Hondas that have excited field (i.e. variable output) alternators. The connectors burn up because the contacts get dirty/corroded creating some small resistance in the connection and with high currents (relatively) the connector pins heat up and melt the shell. Keeping those connector pins clean will help avoid melting issues (I'm as guilty as everyone else for rarely checking until it too late).

Dealing with this right now on my ZN. The voltage output from the stator is now fine (new pins and connector shells) but I haven't check to see if the stator is visibly burnt (will inspect the next time I check the valves). My theory on why the early 1300s burnt alternators is because they marginally had enough oil splashing around in them to cool the alternator to start with and they were oil burners to boot so it wouldn't take much of a lack of oversight on the oil level to reduce it enough so that alternator cooling is affected.

I'm curious if anyone has ever figured out how much more than the recommended oil can be added to early 1300's before the oil starts showing up where you don't want it.

This seems to be a very common problem, particularly for early models. From my experience (5 stators and 3 regulators), the key issues are:
1) Not all stators are equal - the original fit unit was a much higher quality part - the replacements are less robust - see www.kz1300.com/index.php/forum/electrica...ll-stators-are-equal
2) No organised cooling - later models incorporated a cooling channel to direct pumped oil onto the stator
3) The "shunt" type regulator originally fitted ensures that the stator produces its maximum current v's speed at all times - even when not needed. A "series" type regulator ensures that stator current (which heats the stator) only meets demand and no more.

My solution has been to fit the best quality stator I could find and replace the shunt unit with a Shindengen series type regulator (SH775) - see www.kz1300.com/index.php/forum/welcome-n...r-with-1979-z1300-a1 - page 4.





Hope this is helpful

Interesting stuff again Neville,

This is a common problem with many 1300's and I think the main issue as Scotch pointed out is the lack of cooling, yet there are still many owners reporting over 40,000 miles and still being on the original stator.
Mine still puts out 14.5 V at regular running and so far so good !

Pete F
UK