stole this from another forum
this guy is a motorcycle mechanic.
"Well, here's the deal; with the LONG stroke we have, piston speed is a critcal factor. If you increase the rpm limit piston speed will greatly increase. That's a lot to ask for a crankshaft and rod bearings to stop a huge rotating assembly, that traveled that long distance and picked up that much speed; to send it off in the other direction. Plus, my experiences with dyno testing tell me the HP drops off after 4800 anyway. (even less rpm with my DG's) Now, eventually someone may come up with a pipe that flows on the top end better, and we may get up to about 115 hp with stock internals; but after that there'll have to be a cam change, and once again there's the piston speed to contend with. From what I'm learning about this bike, it'll go faster using the torque band than it will using a horsepower curve. But, this is still a new field because no one's ever gone inside one of these yet; so I could be wrong."