Ticking can also indicate that something magnetic has got loose inside the instrument and has lodged in the cup. For practical purposes there is nothing you can do about it other than hope that it wears away and stops.
I disagree with Monte regarding the correct lubricant for speedo cables, my experience tells me that a good Low Melting Point, Molly grease is the thing to use, you get your fingers good and dirty smearing it on the cable, however do not lubricate the last 5 inches or so as you do not want grease working its way into the "works".