TOPIC:

there should be a rubber type seal on top of the engine side of the connection that acts as an oil seal I believe and that should take up the play you are finding. If I recall correctly its more like a square sided O ring that sits in the top of the drive adapter
to help stop oil migration up the cam drive gear.

Don't forget those two weird locking plates that hold the motor side tach drive end in

Gradually losing the will to live, took the tacho drive out to check no splines damaged all the seals seem okay still getting a loud whine and erratic needle ,next stage I will take out the inner cable and lube that,never had to do that and I must have changed 5 cables over my time

any way to check if a bit has broken off one end of the cable more then likely the the head ide as it would just fall down and you wouldn't know it. if the cable isn't making a solid fit into the cluster end maybe that is your issue? ya never know or maybe a bit broke off and is stopping the cable from fitting right and causing it to skip once in awhile.

or bit of dust or crud in the cup between the magnet making it jump a bit now and again ?

Used the bike for work today and 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[if you know what I mean], if you take the nut off of the clock end it seems to stop whining and behave normally but I cant work out why it would do this, sorry if im boring you guys but you are probably the best source of info and experience on z13s there is
thanks again for all your help
Paul