In response to Richard, the dealership in Seattle says the the HP is rated at 10HP but I have seen this posted on ScooterGallerySeattle.com website as 9.8HP. There are 3 different modifications that can be done. One is the carburetor mod that replaces the carburetor and air box for better airflow, this costs $175 for parts and labor. Second one is the CVT kit that changes the weights in the clutch pack to allow for higher speeds, but sacrifices some power on take off and changes the standard belt to a Kevlar belt, this costs $200 for parts and labor. The last mod that is offered at ScooterGallery is the exhaust kit that also helps with better airflow, this costs $325. With all three mods I was told you could get 13HP out of this engine. Oh and Alex also mentioned placing larger valves in the head but I was not interested in altering the internal engine components. I am considering doing just the carburetor and the transmisson kit, as I am in need of more consistant top end speed. The bike tends to dip below 60mph on slight inclines which makes me nervous on SeattleĀ“s highways.