Big Bore Cylinder Unit Ø 85 mm 290 cc HONDA CRF R 250 cc 2018-2023

After the latest developments the original Honda engine is today much improved above all at low speeds. The strong point of this bike is the ease with which it is possible to exploit the power supply. Even an amateur is immediately at ease on the track with a bike like this. However, where you feel the need for something more is starting from the medium revs, without distorting the sweet and soft character that characterizes this bike.

Athena's big bore Extreme brings the displacement to grow up to 297 cc and manages to hit this target: the increase in power and above all in torque is substantial and evident. However, the bike on the track remains easy to manage and remains linear when opening and reopening the throttle.

The final result is therefore extremely enjoyable: an engine with much more strength and body at all rpm ranges, maintaining the inertial lightness of an MX2 unchanged.

The long experience acquired in the world of Offroad and Racing has allowed the R& D Athena to create something that was not yet present on the market: a Big Bore Cylinder Kit with Ø 85 mm steel barrel dedicated to 250cc off-road motorcycles for an increase in displacement never achieved before, without making any changes to the engine crankcases!

The entire kit guarantees maximum performance, better delivery, greater torque at low and medium rpm, better acceleration, better reactivity and at the same time reliability equal to the original thanks to all the technical features resulting from the challenge won by the Athena R&D team: everything combines with the proverbial handling of a 250cc from Offroad for a simply exceptional driving experience.

The kit includes the aluminum alloy cylinder, the forged piston complete with pin and rings and all the necessary gaskets.

The Athena Technical Department manages the entire of the development and approval process of the thermal unit: in fact, it designs together all the elements of the kit which are first tested and validated by its test room technicians and then directly on the track by the drivers. The result is a combination of engine components that ensure maximum synergy between them.

More power, more performance and more fun: are you ready to never get off your bike again?

THE CYLINDER

The cylinder with extreme increased bore Ø 85mm is made of aluminum alloy and with a high silicon content.

To allow such an increase in bore while maintaining the original crankcase, the choice of Athena technicians was oriented towards a steel cylinder liner.

This cylinder barrel is not inserted by pressure inside the cylinder hole but positioned directly in the mold through an innovative co-fusion production process. Thanks to this method, studied and tested internally, the aluminum casting "embraces" the steel making it integral with the aluminium. This allows for excellent heat transmission and an efficient mechanical grip which prevents mutual sliding even after many hours of use, guaranteeing perfect union and reliability over time.

The inside of the cylinder liner is subjected to a galvanic nickel silicon coating treatment developed by Athena and the subsequent sanding, to obtain maximum smoothness and optimal resistance to wear.

The winning key of this new Athena project is to have developed a cylinder resulting from the union of two different materials with particular attention to the study of the cylinder barrel. The upper geometry of the cylinder liner was designed to ensure maximum sealing in the combustion chamber and guarantee the appropriate contact pressure between the components in all conditions, avoiding pressure losses, leakage of liquids and/or gases.

PISTON KIT

The forged aluminum alloy piston is a guarantee of resistance and lightness. Furthermore, processing with latest generation CNC machines ensures perfect geometries and reduced tolerances.

The lower structure has a double open beam to combine greater resistance to fatigue, lightness and better cooling of the piston crown.

Particular care was taken in the engineering phase of the piston crown, optimized for greater resistance, better heat dispersion and optimization of compression ratio to guarantee greater elasticity in driving and reliability over time.

The shell integrates a molybdenum disulphide coating which is applied via silk-screen printing to reduce friction, noise and improve sliding. The segments included are Made in Japan and are made of special steel with a chromium nitride coating applied with a PVD process, to guarantee low friction values, better smoothness and longer life.

The piston pin, specifically designed for this type of extreme application, is biconical and made of alloy of aeronautical steel with nitriding treatment with DLC “Diamond-like carbon” surface coating, which guarantees high hardness and low friction.

SEAL SERIES

The series of seals included in the kit, developed by Athena technicians, is specifically designed for our new aluminum cylinder with steel barrel, to guarantee maximum sealing and durability.

The head gasket is of the MLS type (Multi -layer Steel) designed specifically to respond to increasingly higher pressures and temperatures, it is made using latest generation Laser cutting technology.

The material used is stainless steel with high elastic return for high adaptability to surfaces and to guarantee excellent sealing across the entire surface in a uniform manner. To further improve the sealing capacity, it is equipped with specific reliefs around the cylinder barrel and the oil and water passages.

In the name of the synergy ensured by our internal design process, the cylinder base gasket is also made by laser cutting in stainless steel with a specific rubberized coating.

The rubberized inserts and the relief around the cylinder barrel are the Athena team's design response to effectively and constantly support the cylinder body subjected to the closing load of the head studs.