Bad float needle questions came up a few times recently over on Modern Vespa, and then the Bad Needle Fairy came and visited my Sprint, so I shot some video of how simple and easy diagnosing and fixing a bad float or float needle is.
It's five minutes and a five dollar part. All you need is a flatblade screwdriver and/or 10mm and 8mm wrenches.

Okay...maybe ten minutes if it's your first time, but still, it's about as simple a repair as there is on a Vespa.