APEX TECHNICAL INNOVATIONS CYLINDER HEAD KIT, YAMAHA YZ250/YZ250X 99-25

The Apex Technical Innovations billet cylinder head offers a two piece design made of 6061 aluminum alloy. The two piece design allows for interchangeable combustion chambers (domes) to suit the power characteristics of any riding style. “Best bolt-on mod on the market.”

The SX dome gives a big midrange boost with more power throughout the power curve. If you’re looking for the pulling power of a 450f while maintaining the snappy character of a 250, this is the dome for you. It is best suited to tight tracks with lots of jumps out of corners.

The MX dome comes on the pipe sooner, gives a smooth midrange pull, greatly improves top end power, and extends overrev. This dome works best on fast, flowing tracks.

The XC dome is designed to smooth out the power curve and make the bike more tractable in the woods. It will give you the luggability of a 300 while maintaining the fun factor of a 250.

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 0.050”.

The OEM cylinder head leaves a lot to be desired 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, but we can accommodate requests for race gas domes or for those at high altitude. 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.

Custom domes available, email/message for details

Custom colors include black, gold, blue-grey, clear, red, green, purple, brown, orange, pink and pewter.

Note: this kit contains one replacement gasket set and one dome sealing o-ring per dome.

Most heads are built to order.

Custom colors, big bore options available upon request.

Jetting chart attached for a starting point only.