Speedometers are very optimistic, I friend of mine had his spedometer reading 256 once, and he was really doing about 195 (he has a gsx1000 with an american turbo kit on it, 264 hp dyno tested), so the point is buy a speedometer corrector or a gps if you really want to know how fast you are going, in my gsxr1000 I have seen 192 and that must be about 170, and have never seen a 600 or 750 or 900 near that true speed. Just race with him and show off.
ride safe