2012 Ktm 125 SX, Those seeking the highest performance and most technologically advanced 125 need look no further than the 125 SX. The free-revving and lively two-stroke engine has gained even more performance for the current season. Not least due to the completely new frame and the new, progressive linkage rear suspension, there's no way to avoid the 125 SX — whether making the transition from an 85 cc machine or when planning the career of a future champion.