Tachometer not responsive

Had problems with the 1981 speedometer cluster after taking a spill a few months back. After installing the tachometer it became slow to respond to engine revs. Reads about right at an idle but wont respond to throttle revs. Any and all advice is welcome in advance.
Happy New Year to all.

Sorry to hear about your "spill".

Don't know how bad this "spill" was.......doubtful that the tach. frame got damaged, so would focus on giving the internals a good cleaning. Old lube, dust and insects will cause this scenario.
  DO NOT use high pressure air !  You'll ruin the Hair-spring" !
  Electronic Cleaner in an aerosol can and WITH and Extension Tube  is effective and safer as you can precisely control it's application..  The only lube required would be a drop of oil on the input bushing.  Don't lube anything else !   (This applies to the Speedo in particular) .  When clean, there is no load on any of the internals. Over lubing will just attract dust and grime.
hope this works out for you !

I've used these guys 2x times for kz1300 speedo's and 1x for Honda Accord speedo. They do great work, and do tachometers too.

www.foreignspeedoinc.com

 

I would try a new cable first off, the ends are squared to fit the drive if rounded off with use the cable can slip
when under excessive load