What will happen if people drive motorcycle 1000km per hour?

I will use mph as those are the units I think in.  1000kph = 621.371kph.

I have ridden a bike at 150mph (don't ask why, I have been told how I could have avoided it other than what I finally figured out what to do and trust me it was not my desire) and was holding on for dear life because of the wind against me. 

At about 100mph the wind resistance starts getting pretty high.

At 621 mph, it would be impossible to hang on.  Your motorcycle would have to be enclosed in a shell that applied pressure downward to keep the motorcycle on the road while redirecting all other atmospheric forces around it.  Further the motorcycle would need to be protected from winds blowing in from beneath the shell.  Without all sorts of extra hardware to further stabilize the vehicle, I expect it would crash, for example, I am not sure how the tires would react.  The centripetal forces may well rip the tires to shreds as well as the wheel.  Further it would be interesting to see if the engine would probably exploded first from the rotational forces or the vibratory forces.

As the only vehicles that have achieved or exceeded the speeds you suggest were either rocket (once) or jet (3 times) powered, I would have trouble calling the vehicle a motorcycle with the engines are longer than the rest of the vehicle and the engines have a diameter greater than the height of the vehicle.

Terminal velocity for a human falling in an orientation to cause the least wind resistance possible is about 122mph.  That is 1/5 what you are proposing.