I stumbled across this website for registering top speeds recorded at race events http://www.100mphscooter.com. Even if you aren't into scooters it's worth checking out the speeds that can achieved http://www.100mphscooter.com/100_mph_speeds.html
For example the current DLRA 175cc motorcycle record is 71.574 mph. The top speed on the 100mphscooter is by a nitro assisted 172cc. It got a 119 mph terminal speed timed on a quarter mile run!
I've added my time and so far I am the world's fastest Vespa though I was hoping for much faster