Slow Tacho.............

The Tacho on my 79' KZ1300 has just began behaving.

It will not register above 1500 RPM even when revving the bike.

Cable and worm drive all very good and working, so must be something inside the Tacho Head itself.

Has anyone out there had this issue and found a fix as I have never had the problem on any other 1300?

Regards

Pete F
UK

Just shooting in the dark here brainstorming- if there is a tiny rubber round belt transferring the rpm's, perhaps it's slipping - dirt, wet, grease, slippery after washing, stretched, cracked and no tension?

The tach is no different than the speedometer head. The cable drives a 2 poled magnet inside a cup which is attached to the needle shaft. There's no physical connection between the magnet and cup.
so 1 of 2 things could happen. Either the cable is not engaged at either the bottom drive gear coming off of the camshaft or,
The tach needle shaft is binding in one or both of the needle bearings.
You can check the needle bearings by rotating the needle off of the stop pin and watching the needle as it returns to the stop pin. It should float nicely.
You can check the magnetic drive by placing a piece of a tach cable in the bottom of the tach and spinning it with your fingers or an electric drill at no more than 500 rpm.
Those checks should point you in the right direction.

Interesting,

Thanks for the tips on what the prob maybe.

Another good job for me to look forward to over the Xmas Hols !

Pete F
UK

It must be a coincidence but my 79 A1 Z1300 has just started exhibiting the same symptoms. I only recently changed the tacho cable but have checked the drive and cable and all seem to be fine. I have attached a couple of pics from a web search of what is inside the tacho head and it's exactly as Kawboy states; a very simple but crude magnetic system that uses a magnetic flux to drag a cup against a spring - all very delicate I suspect. This is also a job for me over Christmas so I would be interested in anything you discover...

Looks like mine needs attending to as well.
Any tips, do's/don'ts for cleaning the bearings/mag drive mechanism?
Thanks.