Tachometer seems "sluggish"

[rdsarefun]

I bought another 74 RD350 a few weeks ago and am going thru it.  The bike runs but needs some TLC.  The tachometer seems like it is slow to respond when the rpms's rise (as compared to my 75 350).  I removed all the control cables and lubed these, all move freely within the casings. The tach cable is properly connected on both ends, and "spins" with it disconnected from the tachometer.  Every once in a while while revving it seems to catch up and report what I feel is proper.  Assuming the tachometer is at fault, has anyone seen this behavior before?

[m in sc]

yup.  take tach off. get a cotton ball. put some kerosene on the cotton ball. while holding tach face up, put cotton ball about 1/2 way in bulb hole (illumination one) leave sitting face up for a few days.

the kerosene will slowly evaporate and lubricate the pivot in the gauge.  take cotton ball out and try on bike.  fwiw, tgis is an OLD clock maker's trick. and it usually works

[rdsarefun]

Much appreciated, will try this trick when home from vacation