120,000km A5

Looks like you have it figured out. I'd accept that answer. Makes sense.
Thanks for sharing  this subject with us. Maybe in the future when it comes up again, we can fall back on your findings.

KB

RBY wrote:

 It has a niffty handle that folds out in front of the left rear shock and sure makes getting her on the centre stand a lot easier - I thought these were only on the Voyager frames?

 

That handle isn't a Voyager feature, at least not a North American ZN1300 Voyager feature.  The left-hand passenger grab rail doubles as the 'hoist point' when putting the ZN1300 on its centre stand. 

Feeling a bit silly now as I have just found where the mystery bits of plastic came from, should have noticed as soon as I took the generator cover off. The question now is, does it matter that much of whatever this was, has come off? I don't think it holds the magnets in the rotor or provides any sort of insulation?? Any guidance appreciated.

Would affect the rotor balance, but it might be so small that it doesn't matter??

Maybe it would be prudent then to remove what's left, as I don't want any more of it going through the bottom end?

I see 4 more cracks at the 9:30 - 10:00 o'clock area so they would eventually break off. I also see  areas where the magnetic carbon fiber magnets broke off at the 6:00 and 8:00 o'clock regions..
I think the nylon was encasing the magnets and bonding them to the shell of the rotor. Nylon doesn't like thermal cycles and it's no surprise that it cracked after 40 years. I think it may have been exacerbated by some rough handling in an attempt to remove the rotor from the end of the crankshaft using a method other than the proper Kawasaki rotor puller??