Tach has a slow response

I am at the final stage of rebuilding my 1980 KZ550 and finally got it started and running on all 4 cylinders, it has not run in about 12 years. However when I rev the motor the tach is very slow to increase, it eventually does go up and It is also slow to decrease. The gauges were in good shape and all I did was clean the rust off them and re-paint them, the cable is new and I dripped oil into it when I installed it. I am wondering if the tach needs to be oiled or greased or sprayed with WD40. I would appreciate any advice or suggestions.
Thanks Tomas

Be careful spraying anything in there. If you do make sure you don't do it up side down. It will get all over the glass.
Steve

You should lube the cable, not the gauge. Motor oil works well for the cable. Ed

The tach has a liquid filled drive. Fluid loss symptoms typically start as a a bouncing unstable needle. I guess it could also cause a slow response. The drive is sealed and can't be refilled. As far as I know, replacement is the only option.

Really?
When did these become liquid filled or used a liquid drive and which instruments are built this way?

missionkz wrote: Really?
When did these become liquid filled or used a liquid drive and which instruments are built this way?

The little cylinder between the bell and the needle is a damper with oil in it. When the oil is lost the works are toast.

See www.zresto.com/page2.php and scroll down to the final paragraph and pic.
If you get all the cobwebs dust and any crud out and the cable is lubed and the problem persists then this is likely the culprit. I have a jumpy mechanical tach and can only look for replacement or one I can cannibalise. Until then I live with it

Anyone know what kind of oil is in that little cylinder?
Why couldn't it be drilled with a tiny drill and use a hypodermic needle to fill it back up?

While I know some are filled with oil, the ones I've worked on aren't. They are a weight. They don't spin. The problem I was having is the bearing at the bottom of the needle shaft. I have all but given up on them but in time I will go back into them. Meanwhile I spent $250 + shipping to have something that is plug and play.
Steve

missionkz wrote: Really?
When did these become liquid filled or used a liquid drive and which instruments are built this way?

Bruce, delete this one?
Steve