[ktm450xcw]

So, I'm new here I've had my scooter for about a year, it had a rough life before I got it, and still doesn't have the greatest. it's a Schwinn Valo 150, which from the scooters I've looked at, most of these are all just GY6 motors, seems about everything is interchangeable. my wife has a jetmoto, and my buddy has a tank. acceleration/top speed/RPM seem to be the same on theirs, while my scwhinn seems to have a little higher top speed, way lower acceleration.
I replaced the rollers, (never weighed the old ones due to the fact that they had flat spots wore into them I didnt' figure I'd get an accurate weight) put some 10 gram weights in and nothing seemed to change. I also put the 1500 RPM springs in, and the only difference was the clutch engagement point, which I figured.
the belt seems to look good,(comparing it to snowmobile belts) everything looks well lubed, I just can't figure out how to get the acceleration out of the thing? what am I overlooking? any help would be greatly appreciated.