I also posted this vid a while ago, along with a GSX-R 600 Turbo vid. Here's the story:
The bike in this, as already said, is a turbo hayabusa. The outside numbers are in MILES, not km. It is very easy to tell this because you can see that the inside numbers go to 3 digits when the outside ones hit ~60. As 100 km/h ~62 mph, it's easy to determine that. Also, as to the question of why he slows down and then the speedo drops, the answer is very simple. If you watch, you can see that when the speedo maxes out, he's only hitting 10k rpm on the tach. He keeps accelerating to 11k rpm, which would make his speed also 10% higher than read, or ~242 mph.
In reality though, the guy changed the gearing on his bike, and corrected the speedo ratio so he can read off his correct speed, but left some kind of switch so the speedo will read what he WOULD be going with the stock gears and the rpm off the tach. I think his final top speed in this video was about 202 mph. Still hella fast, but not quite as impressive as what we are led to believe
(I loved the 50 mph to 140 mph wheelie in ~4 seconds

)