Thought I'd post this in case it happens to anyone else. (I've had loads of tips from this site and wanted to 'give back')

I'm in the process of restoring an 04 Vespa ET2 with my son. When we came to check the hub oil we were foxed by the apparent lack of dipstick, but then we realised the top section had sheared off leaving the rest of the dipstick in place but irremovable. Someone must have tightened it with mole grips or something similar.

What I did was drill a small pilot hole in the stub, its only plastic, then used a small bolt extractor (aka "Easy Out"), and very carefully removed the dipstick. I was paranoid about chewing it up and leaving fragments of plastic in the hub.

I'm glad to say this worked a treat and the replacement dipstick screwed right back in there.