Put a GPS on it and report back. Top speeds are one of the most lied about, and misquoted, estimated things known. Makes fishermen look honest. Estimated does not fill in for factual readings.I had an R3 which has a 321cc engine and the top speed is anywhere from 103-110 mph.
Wind resistance is the big issue. Some bikes cut thru the wind better. We used to run 250 cc Yamahas with 45 HP to 120.
They had very good full fairings. I will stick with my 45 HP will nudge 100 on a good day, and Saturday night.
As an aside, my 49 HP Norton did 108. Advertised as 120. UK