ANY bike in top gear should actually be showing less revs than the speed. So at 50, revs should be about 4k, at 60, revs should be about 5k, at 80, revs should be about 7k.
That's because your sixth gear is like an overdrive - the ratio is probably about 0.8:1 whereas fifth gear is likely 1:1.
You've not got a missing sixth gear have you?
Tom