Well, modified ones (turbochargers and more fitted) have set records of up to 259 mph / 416 km per hour.
But an ordinary Hayabusa, that you buy in the shops without modifications would not be expected to be able to exceed 175-185 mph. That's still more than 100 mph over the speed limit in any sane country, so be sensible.
It's often quite hard to stay on the bike at speeds over 180 mph (even the best built and most stable motorbike shimmies at such speeds).
But an ordinary Hayabusa, that you buy in the shops without modifications would not be expected to be able to exceed 175-185 mph. That's still more than 100 mph over the speed limit in any sane country, so be sensible.
It's often quite hard to stay on the bike at speeds over 180 mph (even the best built and most stable motorbike shimmies at such speeds).