Highest speedo reading on my modded AP50 (changed gearing, ported, jetted, air filter, skimmed head, modded exhaust) was 69mph down a friggin' great long dual carriageway hill, flat on the tank, slip streaming a van. Nipped up as the van driver went for the magic 70 and had to whip the clutch in and coast off the conveniently placed slip road before restarting it and riding home a very rattly 'ped. Yet another top end rebuild!
On a level road with little wind, top speed (according to the speedo) was 57/58 on a good day - obviously this was with your chin on the speedo and feet on the pillion pegs but then that's how they were ridden practically everywhere ; )