When my daughter was 17 she bought a Piaggio NRG 50 to travel to work on, 27mph on the flat, maybe 35 downhill, we bought a sports exhaust, without the restricter in the header pipe, and took the restricter spacer out of the variator, resulting in 45mph on the flat, 50+ downhill, illegal, very, but a damn site safer than 27mph with buses and lorries trying to overtake her.