Modern Vespa

Does the silver rim and front glass come off on a PX speedometer (px200 2003) or do you have to replace the whole unit?

The ring and glass can come off (be replaced).

Undo the four screws holding the top of the headset on. Then go down to the bottom of the fork and push (feed) the slack out of the speedometer cable. That separates the top of the headset.

Then get inside, undo the round ribbed speedometer cable nut and metal bracket, and bulb wire. The unit then pops right out

The ring is crimped over the bottom edge of the speedometer unit casing. Gently pry it up all around with a pick or small flathead screw driver until the ring, gasket, and glass come off. If the ring and glass are wasted, buy new parts.

Reverse the process.