it can be pulley swapped on the engine side, that's not saying it's going to do much good, over driving a hydro will most likely destroy it in a short amount of time, in my experience there's only 2 ways to get more speed out of a hydro and make it last, one is bigger tires, not much speed to be gained here but you can get a few mph more depending on the tires size, the other is to relocate the hydro and run a chain drive off the axle shafts to a solid axle that is positioned in the original location, red neck computer geek did a video showing this very thing, from there you can play with the sprockets and gain speed, I personally like a hydro for trail use and light mudding, in my opinion they offer superior control in trails where you have steep hills and rough terrain and would be generally riding at a slower pace