because a 40hp 125 is all you need
found this gem floating around a 125 site
Michael Barnes on racing 125’s
To excel in racing, you first have to learn the basics. And what could be more basic than a 125cc Grand Prix bike? With a single cylinder pumping out a humble 40 horsepower, and a dry weight of just 160 pounds, 125s would seem the perfect beginner's bikes. But that doesn't mean that more experienced racers can't learn anything from them.
"You can learn riding skills on a 125 GP bike that you just can't get from any other machine," affirms Michael Barnes, who has an uncanny knack for hopping on a Honda RS125 and winning national races--indeed, Barnes won a WERA Formula III national the first time he rode one of the diminutive machines.
"The main thing that 125s can teach you," continues Barnes, "is how to squeeze every possibly bit of speed out of a motorcycle. It really teaches you how to soak every last bit of aerodynamics, jetting and gearing. gearing is really critical, because you need to be exiting every turn with optimum speed and rpm to get a good drive, or you'll loose precious seconds that just can't be made up on a straight. And since, on a 125, you're drive is almost solely based on your cornering speed--which is, in turn, based on your entrance speed--you will quickly learn how to tie all aspects of speed together. And that helps your overall riding, no matter what machine you compete on.