125cc Gearing and Sprockets

This is the most overlooked and cost effective way of increasing your motorcycles power. For the price of a tank of fuel, you can increase your top speed by 30% or almost half your 0 – 60 times. Gearing is very important, and needs to be adjusted to suit what you want and your style.

Here are the basics; you will have to experiment on your own to get what you want: Bigger front sprocket = slower acceleration, but higher top speed. Also, better fuel economy (if that concerns you…) Smaller front sprocket = quicker acceleration, lower top speed and worse fuel economy. The opposite is the case for the rear sprockets, smaller rear – better top speed, larger rear – better acceleration.

Bear in mind, when altering the gearing that you may have to adjust or even change the chain to accommodate the different sprocket sizes. And also consider, a relatively small change can have quite an effect. The general advice it only change one tooth at the front, and no more than 3 at the back i.e.. go from a 16t to a 15t front sprocket at the front for better acceleration. One last consideration when changing the gearing, which does not affect some 125cc bikes, is that changing the gearing can alter the speed your Speedo will show; so check this out on your model before fiddling.

Renthal are a top sprocket company, and Afam are pretty good to.