Everyone has there own view on this but my experience with smaller bikes is that they are often over geared. The engine doesn't have the torque to hold top gear at high speed. Fitting a smaller front cog just one tooth less can transform performance. Not only increasing acceleration in all gears but enabling the engine to be at the right rpm to hold top gear better. In theory the overall top speed is decreased of course, but in practice I found it enabled me to hold higher speeds. I was forever revving it in fifth, then into sixth, at which point is slowed down until I was back in fifth again. With the smaller cog it could hold sixth against the wind resistance and even climb modest gradients. As factory my 125 rarely got over 60, with the smaller front cog it would cruise at 65 hitting the limiter at 68. Hence slipstreaming wagons made life more comfortable, if at times somewhat geographically challenging. Interesting, mine hasn't been completely run in yet, about 60 miles on the clock, but i have had it to 60 mph, with plenty of throttle left, but until it's run in , i can't really see the top end performance, but the lower end is pretty quick for a heavy bike, but i do need to get the rev's up, also there is no rev counter, which makes it impossible, or the very least difficult to judge rpm's, plus there is not much in the way of general info about it, which doesn't help with research, the jjoy's of biking