Speedos are not accurate & are invariably optimistic. I seem to remember that the ZZR1400 in tests was topping an indicated 200+ but was actually doing the max restricted speed, so you were probably a couple of MPH shy of 180. Sat nav is supposedly a better indicator of true speed. Or take it to Bruntingthorpe & do some timed speed tests. Apparently on the ZZR there is a connection on the gearbox that can be overridden to give a single unrestricted run.