50cc will go 40-45mph all day & top out @ 50 or so...52 on a down hill ;-)
The scooters w/ 150cc or more will go the speed limit on most freeways. Anything over 50cc you need a motorcycle license for though. I get a kick out of cruising around with my brothers and friends...good times. Since you can pick-up a used one for between $500 - $1,000...it's plenty of bang for your buck. The wife can even hop on the back and you can mob around euro style :-)