High pitch whine when accelerating
 

What would cause a high pitched whine from an accelerating scooter? It's not happening to mine but I passed another scooter and it was making this awful sound. It was not a normal sound you want to hear from a bike.

Anything from a gap in body panels to a bearing about to fail. sadly there just not enough info to give you a good answer.

The sound only happened when he was catching up to traffic. I didn't hear it when he was driving at a consistent speed or stopping. I wasn't beside him for long.

Still not enough, location would help. (And not he was heading to McD) Like is it from the front end, or top of his helmet

Probably just the gears in the transmission. They whine a bit under load, some types make more noise than others.

I was riding this past weekend with a bunch of rucks,groms,zuma's, I think it was a zuma 50 that when coming to a stop, or on the hard decelarations you do going down mountain roads,working the hairpins.
It would whine down.
The groms were absoluty awsome machines!!
If I was a younger man, this would be my choice for a small motorcycle as I do miss the gear changing at times.