Complex sentence: Before the start of a race (either SuperBike Championships or MotoGP), the riders have to pull up onto their grid and wait for all the other racers to take their places on the line.
Split into simpler sentences: Before the start of a race either SuperBike Championships or MotoGP, the riders have to pull up onto their grids. They then have to wait on the grid for all the other racers to take their places on the line.