I dont know much about vespas, but I have a Yamaha Vino. They are now 4 stroke but if u get a used 2-stroke it can be made to do about 37 on flat ground and around 40-43 on slight downward incline by just derestricting the exhaust and removing a washer on the belt drive. In order to cruise around 50 mph you could invest in a 70cc kit, which would let u cruise around 50. In order to not have a liscence and insurance it has to be under 50cc and not exceed 30 mph.