When I rebuilt my tach and speedo I used PJ1 chain lube. Sprayed some in a cup and used a tooth pick to apply it to all pivot points and the gears. Once the carrier evaporated it stays put even at elevated temps when the bike may sit in the sun. What ever you use, use it sparingly. Don't forget the hub where the cable attaches. The receiver/housing can squeal pretty bad if not lubed.
-P.
