Modern Vespa

Hi guys. If anyone can help me with regard to installing the speedo gear on my Sprint I'd really appreciate it. I ave tried once and failed. The speedo worked for about a minute. Also, strangely, when I checked it out after I noticed that the cable turned when the wheel was turned backwards but not forwards. I also completely munched one gear cog in my first attempt. I can't find a video anywhere on line either which seems strange.
Thanks a million.

remove the cable at the bottom and the cable mounting on the hub you should see the top of the speedo drive gear turn the wheel slowly backwards this should push the gear out enough to get it with long nose pliers remove when you fit the new one spin your wheel slowly forwards to seat the gear

also if you ever remove the front spindle/axle you need to remove the speedo drive gear first otherwise you'll mash it
hope this helps

Much appreciated