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Overview:
Beta has added two new motocross models to join the big brother 450 in the RX range. All-new 250 and 350 RX 2 strokes are the new 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: All new for 2026, this new model replaces the 300 version for the 2026 season. New 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 new 350 motocrosser will thrive in many different track conditions. Clearly in a class of its own!
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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.
FEATURES
Kayaba (KYB) Suspension
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.
Suspension
Closed cartridge 48mm KYB front fork and the rear shock have been updated with new valving for better overall performance. 50mm shock body reduces the oil temperatures under extreme use during long motos.
Sub-Frame & Filter Box
Aluminum gives the right level of stiffness to the structure. Light, yet 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.
New Aluminum Sub Frame
Similar to the 450 RX the sub frame on the 250-350 RX is fabricated from aluminum for more strength.
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.
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.
Bodywork
Get the frame now incorporates a cast-in brace to further strengthen the frame around the steering neck area. This increase the reliability and stiffness of the frame's area most subject to stress.
| STROKE | 73.6mm |
| DISPLACEMENT | 351.7cc |
| COMPRESSION RATIO | 12:45:01 |
| EXHAUST VALVE | Beta Progressive Valve (BPV) |
| IGNITION | AC-CDI Kokusan |
| SPARK PLUG | Dual MR7VBI-8 |
| LUBRICATION | Pre-Mix |
| FUEL SYSTEM | Keihin PWK 38mm |
| CLUTCH | Wet Diaphragm-style |
| TRANSMISSION | 5 Speed |
| FINAL DRIVE | O-ring chain |
| FRAME | Molybdenum steel / Double Cradle w/ quick air filer access |
| WHEELBASE | 58.7" |
| SEAT HEIGHT | 37.2" |
| GROUND CLEARANCE | 13.4" |
| FOOTREST HEIGHT | 16.6" |
| DRY WEIGHT | 220.5 lbs (wet weight, no fuel) |
| FUEL TANK CAPACITY | 1.5 US Gallons |
| FRONT SUSPENSION | 48 mm KYB AOS Closed Cartridge with adjustable compression & rebound |
| REAR SUSPENSION | KYB 50 mm body with adjustable rebound and high/low speed on compression adjustment |
| FRONT WHEEL TRAVEL | 12.0" |
| REAR WHEEL TRAVEL | 11.8" |
| FRONT BRAKE | 260 mm floating rotor |
| REAR BRAKE | 240 mm rotor |
| FRONT/REAR RIM | 21" (Front) 19" (Rear) |
| FRONT/REAR TIRE | 80/100 | 120/80 |
| SPECS | *Specifications subject to change without notice. Additional information on all models including manuals, accessories and parts books are available online at www.betausa.com under SUPPORT |
