Found this in a 2009 cabe thread, ‘I do clock repair for a living. The center spring is the same as a balance spring on a small clock. The brass wedge is what holds the end of the spring at the outer edge. On the arbor, the spring is mounted in a brass split collet. Put a small screwdriver in the collet, and you should be able to work the old spring off by moving it back and forth and pulling at the same time. Then get online and do a Google search for Timesavers or Merritts Antiques. Call them, and tell them what size the spring is. Springs are measured by length, width, and strength (thickness). You can get a close enough appoximation of length with a piece of buttonhole thread wrapped in the srpring, following it around until you get to the center. If necessary, order a spring that is too long, rather than too short. The effective length will be what is between the block and the arbor, so you can always stick more through, and clip it off after you have the proper calibration on the speedo dial.
I have repaired several motorcycle speedometers this way, with acceptable results.’
