Wayward rev counter

My '69 S has a rev counter issue. Needle flicks from 0-8,000 and back constantly.

Is it the rev counter, transducer or maybe an earth? Any ideas please? Thanks Matthew

I am having a similar problem with my tach at the moment
if I rev to say 5000 the needle doesn't know where it is for about a minute
if I hold a steady speed of 2200 revs - about 60kph - its ok
my mechanics have removed the tach and put in a test tach and report there is nothing wrong with the tach
they have also connected an additional wire to the cdi - a Parts Klassic one - but it seems to make little difference
the swinging tach needle has been there for a while now but has gotten worse over the last month or so
any further ideas ?? :confused:

TIA
Dennis :)

Check your ignition points for gap and cam lube.

Thanks....have just checked at set to .012" assuming it is a Bosch but it may not be and I would rather not take it out to see if someone on here knows (I am sure they will!!) - not quite sure which dizzy I have...Bosch or Marelli. Picture attached - it may of course be a rogue one as it doesn't look like any of the pix in my manual. Any ideas anyone?? ThanksAttachment 507730

That's a Bosch, without the rev limiting rotor.

Excellent..thanks....perhaps 7,300 wasn't enough!!! At least my points are set correct. The rev counter was a bit more settled to start with but then went haywire again. I will try points again but suspect they are ok. Any other ideas?? Thanks Matthew

If you haven't already done so you'll need to put some special cam grease on the distributor lobes, running dry could lead to point bounce and tach reading problems. If you've already done that, and tach still bounces it probably indicates dampner unit in tach head has gone bad. For that you'll need to send to instrument repair service.