NRG 900
The NRG 900 is the fastest motorcycle in GTA IV, and is very close to being the fastest land vehicle in the game. It excels at stunts and tricks, and is the only superbike in GTA IV. It is, however, difficult to turn.
The design is similar to that of the NRG-500 from GTA: San Andreas.
There is an NRG 900 dealership in Alderney around the border between Westdyke and Leftwood.