Every motorcycle, and both other motor scooters, I have owned have had inaccurate speedo. I am a recent convert to scooters, and love my XC500, which is named Puff, in case you're interested.
My '07 XC500 is real close, if not on the money, to what hgw75 posted. I clocked mine by one of those roadside radar things that show your speed. My '07 now has over 16,300 miles on, about 14 months old. Still runs great, and I think the Motorcycle shop - which is my local Kymco dealer - is the best. Many times, they have performed extra services without nickel and dime-ing me to death.