450 RX:

Proven through races all over the world, including the USA Supercross series and MXGP. The 450 RX provides a ride like no other, quick turning yet stable; powerful yet easy to ride, are just a few things the press is saying about the 4-stroke model. An engine with enough power for a top-level pro rider while providing the right amount of power to the amateur as well. For 2026, the 450 RX receives a new cylinder head with improved flow that provides even more power. This, along with a matched intake manifold and a new exhaust, means the 450 will still bark with power but do it in a quieter way. A redesigned counterbalance shaft to reduce vibration and new mapping to go with the new cylinder head and exhaust.

Additional Features of Each Model:

450 RX 4-Stroke

Engine: The 450cc engine development was focused on providing riders a significant performance increase compared to the previous model, offering a stronger torque curve that can be used under all conditions. This achievement was possible due to a new cylinder head with a performance-enhancing piston, a new intake manifold, and a different exhaust system. The head’s overhaul - developed through CFD analysis and many flow bench calibrations - includes an improved intake duct to enhance air circulation inside the engine. The new manifold, following the flow line, has a longer internal horn to improve the tuning of pressure waves, and thus increase their fill while intaking air. The piston includes new coatings to reduce friction and improve its performance. A newly designed counter balancer was introduced to contain vibrations and reduce rider fatigue.

Exhaust system: the head-pipe has been redesigned to create a greater flow and to provide increased power. This new 4-stroke exhaust system is completed by a silencer, redesigned with HGS to contain the DB output, in line with the new racing standards.

Maps: Updated to perform better with the new motor configuration, with renewed start-up and limiter strategies. 

250-350 RX 2 Stroke 

Engine: Both engine capacities received a completely new, purpose-built engine. The 350 RX was designed to obtain the greatest linear power delivery and give riders the option to exploit the great power available when needed, while the 250 RX can count on explosive performance, ready to compete in races under all conditions.

» Head: The first noticeable difference when looking at the new engines is certainly the dual-spark-plug head on the RX 350 2Str, while the 250cc still relies on a classic single spark plug. This differentiates the two motorcycles’ character even further, with the 250cc providing riders with a high-revving engine that competes with the likes of 250 4Str bikes, while the 350cc manages to keep a greater torque and rounded delivery, enhancing its ease of recreational use, at lower speeds while still provides enough overall horsepower for race use. 

» Cylinder, piston, and power valve: to further differentiate the two bikes, apart from the obvious engine capacity, Betamotor engineers worked on new cylinders and pistons, designed specifically for each engine. The power valve, too, was calibrated accurately to manage the two deliveries by adopting different springs.

» Crankshaft: the two motorcycles have a different stroke, with the 250cc reaching 72mm and the 350cc reaching 73.6mm. 

» Crankcase: new engine crankcases, with different internals between the two capacities, matched with each model’s crankshaft.

» Gear box: gear boxes are shared between both models, with the only difference being the final ratios of the sprockets, 13/50 for the 250 and 13/47 for its big sister.

Exhaust: also new for both models. Exhaust systems were designed to enhance the features of both engines, and differ in the internal silencer diameter, which is bigger on the 350. 

New components shared by all RX Models: 

Graphics: a modern race look, simple yet bold, the final touch to the Italian RX range.

Radiators: their bearing structure was strengthened to prevent any deformation that might affect their operation, even during heavy-duty use.

The following elements are confirmed on the entire range:

Frame: geometry remains unchanged, yet the frame now incorporates a cast-in brace to further strengthen the frame around the steering neck area. This increases the reliability and stiffness of the frame’s area most subject to stress. 

Aluminum rear sub-frame and dedicated filter box: aluminum gives the right level of stiffness to the structure. Light, yet it has the rigidity to overcome the demands of motocross. Access to the filter remains on the left side of the bike, and is extremely easy and intuitive, as well as being tool-free. The push button seat also removes without tools.

Kayaba (KYB) suspensions: fork (48mm) and single shock (50mm) are specifically calibrated on the new range models, focusing on their rideability and stability when the pace rises. The resulting setting is enough to make any rider confident, from amateurs to professionals.

Nissin braking system: with floating calipers and 260mm Galfer discs at the front and 240mm at the rear, for powerful and modular braking.

Chain: non o-ring, lighter and smoother.

Lithium battery: lighter and a must for quick starts.

Handlebar silent block: Xtrig Flexfit bar mounts provide a comfortable grip on the handlebar for enhanced control and reduced vibration.

To complete our round-up of the bike:

Engine maps: all the RX models are equipped with two specific engine maps (wet and dry), while the 4-Stroke model has also four levels of Traction Control (on/off/active with hard map/active with soft map) to manage the vehicle's significant power in all terrain conditions. The button to select the map and TC is located on the handlebar bumpers.

All RX will be supplied with a triangle stand. In addition, the 4 Stroke has four different throttle pulleys to customize the accelerator’s response.