tacho cable routing

Playing thee devil's advocate here, you put on a new cable and now you've got a problem. Have you got the old cable still? I would check the old cable outer sheath length to the new outer and also the inner cable length to the old inner. Sounds like you new cable inner is too long and you're binding up the new inner cable and it's winding up and releasing which would show up as a fluttering needle.

God how I love diagnosing things blind!! It's actually insightful. Keeps us on our toes you know. THANKS!!

Thanks Kawboy
I think the problem started before I installed the new cable, the old cable snapped but just prior to this the whining started and the erratic needle and I put 2 and 2 together and assumed it was due to the fact the cable was on its way out, I intend to drive to work today with the top nut undone and see how it behaves
Paul

All good points everyone but Pauls latest comment:

<...the needle spun right around the clock a few times as if it was doing about 15000rpm actually hitting the stop on the wrong side...>

would have me believe that there is something inside the tach itself causing the problem. I say this because as we know the tach (and speedometer) needles are driven by magnetic coupling. The only way the needles can go around and hit the stop-pin is if a piece of foreign material gets stuck between the two internal rotating parts or if something is worn allowing the two parts to pyhsically touch and act as a solid coupling....if you know what I mean. The fact it's happened immedaitely after changing-out the cable may be purely coincedental and we ALL know how that gremlin behaves !

Paul: if you're convinced the cable is good you're going to have to remove the outter instrument housing, re-connect the cable securely with the nuts, start the bike and look and listen. I believe you'll find a "bug-carcess" or part there-of caught between the two impulse-coupled parts. The other concern would be a worn bushing in the Tach-end where the cable attaches or on the inside driven componet. Hopefully it's simple, like foreign material.

I'm using kawboys approach here - the blindfold method. I'm finding the darkness keeps me calmer

Guys
I am going to try another tacho, if its not that is there any way the tacho drive could be causing any of these symptoms

Found a good picture of the inside of a tach. Not kz1300 but so closely resembling ours it could have been made by the same instrument manufacturer.

Picture was unceromoniously ripped-off and posted here without written of verbal permission from "Scca28" on "motorcylceforum.com". Thank you !

Thanks Scotch
will I be okay to clean the top of the magnet face or is it coated in anything, forgive my ignorance but I have had and run z1300s for nearly 30 years and have always changed the tacho cable in 5 minutes flat without any issues , im not sure if its my old age or the bikes but its frustrating to say the least
all thanks to everyone for your help its much appreciated
Paul