The new engine kit has been developed in cooperation with YAMAHA RACING and it is a result of their extensive knowledge combined with their GP racing experience. The target of the kit is to improve the overall performance of the production YZ125, whilst specific attention has been paid to ensuring that a high performance level is reached, without sacrificing engine durability on heavy racetrack conditions. Fitment: GYTRļ¾® recommends that the High Performance Kit is only fitted to a brand new 2019 YZ125 or, where an older model is used, the engine has been freshly overhauled to ensure performance and durability*. This means a YZ125 from 2019 and older can also make use of this kit.