Not all stators are equal

Just a warning note for all of my fellow A1 owners - the original without the stator oil cooling jet. I am now on my 5th stator and have learned the hard way about what works and what does not. My original fit stator lasted from 1979 until 2008. This is the upper stator in the picture below. Without any form of organised cooling, the stator tends to pyrolyse the oil mist around it which eventually reduces any cooling effect due to the thick carbon coating. I replaced the original stator with an aftermarket stator shown bottom right in the picture. I have now had three of these fail since 2008 after a few thousand miles each, due to failure of the soldered joints that connects the yellow stator fly leads to the windings. at high engine speeds (motorway driving generally), that part of the stator gets hot enough to melt the solder. I tried to address these symptoms by trying to reduce the load on the stator - assumed to be caused by a low voltage at the regulator voltage sensing wire (the extra brown wire the connects to the regulator). I overhauled the ignition and main switches to reduce the voltage drop to the brown wire - this did not make much difference - and then installed a relay to the charging circuit - see "New Member with 1979 Z1300 A1".

None of these fixes seem to solve my problems so after the third failure of the stator type shown bottom right, I bought a more expensive version from Electrex, bottom left in the picture. This differs from the cheaper version in that it does not have soldered fly leads (like the original fit) and I also measured a slightly larger winding diameter - increasing the diameter from 0.9mm to 1mm does not sound a lot but this increases the cross sectional area of the wire by about 20% which means 20% less I*2R heating losses for a given output voltage. The inner diameter of the Electrex stator was a little too small and needed some dressing to fit but otherwise has so far solved my charging problems. The cheaper stators may be OK with the later models with the oil cooling jet but I suggest that all A1 owners avoid this type of stator.

I originally fitted a voltmeter to monitor how the charging circuit was operating - however, this was giving me too much information and I was reading too much into small (0.1 volt) changes in voltage. I subsequently fitted a SparkBright Eclipse LED indicator to the instrument cluster. I fitted this next to the ignition switch rather than the spare (EU Model) headlight warning light position as there was not enough room for the small circuit board behind the LED and I also wanted to avoid any flashing lights next to the oil pressure light. The LED has a number of modes - below 12.45 volts flashing red but above 12.45 and less than 13.2 volts, steady amber - this is what you should see without the engine running.

With the engine running and charging, anything above 13.2 volts show steady green.

It shows green/red alternating if the voltage goes above 15.2 volts to tell you that your regulator has some serious issues. I have found this indicator to be a very useful addition providing peace of mind that the charging system is working as it should.

Awesome information Neville.Thanks for taking the time to share. I like the simple LED monitor too. Where did you source the SparkBright Eclipse LED indicator ? So simple and takes up next to no room on the cluster. Well done !!

Thanks! It available on line at: www.sparkbright.co.uk/sparkright-eclipse...-voltage-monitor.php - I bought the Eclipse5 (auto dimming in low light) and it cost 16 UK pounds + postage at 1 UK pound. It was a bit tricky to drill the hole in the instrument panel cleanly - the front face has a clear plastic facia in front of the black plastic housing with a small air gap between - if you are not careful, you will get plastic debris from the drilling process in the air gap and it is a real pain to get out. I used a very powerful vacuum to suck it out through the drilled hole and then sealed up the gap around the edge of the hole with silicon sealant.

This is a great idea and an inexpensive piece of mind given my current charging issues and ongoing diagnostics and repairs.

I'm a bit confused about the "Oil cooling jet" for the stator. Can't find any reference to it in the manual. With the stator mounted to the cover and being fully enclosed/surrounded by the rotor: Where does this "cooling oil" come from?

Using the recent reference I revisited the "melting solder" concern.


Shame on the manufacturer ! To simply drop the 3 wires between their respective pair of widely gaped posts is almost negligent ! The posts should have been squeezed to physically trap the wire - Then soldered. Probably won't address the melting solder concern if there's issues creating this much heat but would make for a more viable connection, regardless.

The information about the oil feed was in the Technical Articles from the original KZ1300.com website. I don't have this electronically but I did print it out and have attached a copy of the relevant page.