Specs

From the dealer's page

Beta has added two motocross models to join the big brother 450 in the RX range. 250 and 350 RX 2 strokes are the bosses in town! Beta’s 450 RX has been racing on the world MXGP tour for four years and the AMA USA Supercross series for two and has proven to be a serious contender. The Italian Beta engineers decided to “Go Big” for 2026 and add not only a 250 cc bike to race in the proper classes but also added a 350 RX smoker as well for everyone else! All Beta MX models are designed with the trademark RideAbility in mind. A motorcycle that is overall easier to ride. 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 cylinder head with improved flow that provides even more power. This, along with a matched intake manifold and a exhaust, means the 450 will still bark with power but do it in a quieter way. A redesigned counterbalance shaft to reduce vibration and mapping to go with the cylinder head and exhaust. 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 cylinder head with a performance-enhancing piston, a 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 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 coatings to reduce friction and improve its performance. A 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 4-stroke exhaust system is completed by a silencer, redesigned with HGS to contain the DB output, in line with the racing standards. Maps: Updated to perform better with the motor configuration, with renewed start-up and limiter strategies.