Specs

From the dealer's page

Beta has added two motocross models to join the big brother 450 in the RX range. All 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 model 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. 350 RX: For 2026, this model replaces the 300 version for the 2026 season. Engine cases, bore and stroke, as well as a twin-plug head to ignite the special power only a big-bore 2-stroke can provide. The longer crankshaft, combined with the final gearing ratio of 14/47, provides a large amount of torque and overall horsepower that will turn some heads. This 350 motocrosser will thrive in many different track conditions. Clearly in a class of its own! 250-350 RX 2 Stroke Engine: Both engine capacities received a completely, 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 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 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.