Press room

Athena presents the new 2019/2021 Yamaha YZ85 Big Bore cylinder kit

3 November 2021

Alonte (VI), Italia, Novembre 2021. Athena is pleased to present the new big bore cylinder kit, developed for Yamaha YZ 85 2019/2021. The kit increases the displacement to 105 CC and significantly improves the original engine’s performance and efficiency, also guaranteeing extreme reliability and optimal sliding properties.

In addition to the cylinder and the complete piston, the Big Bore kit contains the modular head and all the gaskets needed for assembly. The Athena cylinder kit can be installed without any changes to the motorcycle crankcase and without having to replace the original engine components.


All the components of the kit have been developed to withstand the highest temperatures, pressures and stress. Furthermore, Athena carefully selects the most suitable material for each application, such as the cylinder head insert, specifically made of bronze and not of aluminium like the original. This modification ensures better thermal stability even at high temperatures.


Another distinctive feature of this kit is the special power valve system that allows for higher performance at medium and low revs, both in terms of horsepower and torque.


The cylinder of this new cylinder kit provides further benefits. Made of aluminium alloy, it includes a nickel-silicon coating on the sleeve that ensures ideal sliding properties. It also guarantees better distribution of the clamp load compared with the original Yamaha thanks to the use of 6 equidistant studs.

Last, but not least, the modular cylinder head with inner bronze dome ensures maximum flexibility in customising the compression values.

From the technical data on the test bench, this kit allows you to exceed 23 HP, and it is available at a manufacturer’s suggested retail price of €899.99.