>>28609868
Hp is a unit of worked defined by the mathematical formula torque * rpm/5252. A 900cc three cylinder has longer strokes and marginally heavier pistons. It's not going to rev as high. A bike with a flatter torque curve is going to require less shifting to stay in the usable powerband and will help riders be more consistent with their laptimes. 600cc was just a racing displacement limit. If you're shooting for a general hp target and have no a higher displacement limit, sometimes less cylinders, longer strokes is better. Nobody dunks on the RC51 for not making as much hp/L (completely stupid metric btw).