Fitment: 2005-2023 YZ125 / 2020-2023 YZ125X

The SX/XC dome gives a big midrange boost with more power everywhere on the front side of the power curve. It is best suited to tight tracks with lots of jumps out of corners.

The MX dome greatly improves top end power and over-rev at the expense of some low end. This dome works best on fast, flowing tracks.

All three domes feature combustion chambers that are fully optimized (compression ratio and MSV) for their specific riding conditions and have a nominal squish clearance of 0.035”. The OEM cylinder head leaves a lot to be desired (see our FAQ), and it’s large squish clearance can lead to jetting woes, detonation, poor fuel economy and throttle response, and less power. The Apex Technical Innovations head solves all of these issues while giving you an increase in performance where you need it most. All three of our standard domes are designed to run on pump gas.

Finally, the two piece design allows for higher coolant volume and flow was specifically designed to remove heat as efficiently as possible. Combine this with the higher thermal conductivity of billet 6061 aluminum vs billet 7075 aluminum and cast aluminum alloys, and you have a recipe for a powerful, usable, and reliable engine.