RX 250 F

My27

Beta’s official debut in the MX2 class with a 4-stroke. The new RX 250 F is designed to offer the perfect balance between top-level performance and rideability, thanks to an extremely compact and lightweight engine unit — approximately 1.5 kg lighter than the competition’s standard — and advanced racing electronics featuring Quick Shift and Launch Control for maximum effectiveness on the track.

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249,8 CC

Displacement

78 mm

Bore

101 kg

Dry weight

340 mm

Ground clearance

Main features

SUSPENSION

KAYABA SUSPENSION:
MX2-SPECIFIC TUNING

The suspension system relies on the KYB front forks and rear shock, already successfully used on the 450, but here equipped with a specific setting developed to adapt to the character and masses of the compact 250 powerplant. Contributing to completing the chassis package is a targeted choice on the wheel front as well: the rear rim features a narrower cross-section compared to the other models in the range, with the precise objective of reducing rotating masses, increasing the overall agility of the vehicle, and limiting power losses when putting the horsepower to the ground.

ELECTRONICS

LAUNCH CONTROL AND QUICK SHIFT: RACE-READY TECHNOLOGY

The responsiveness of the new 250cc engine is supported by superior electronic management derived directly from the world of racing. The introduction of Launch Control, adjustable across five levels of intervention, optimises traction at the starting gate to maximise initial acceleration. The system works in synergy with the all-new Quick Shift, which allows higher gears to be engaged without closing the throttle or using the clutch, ensuring optimal gear-change smoothness and constant forward thrust.

DUAL INJECTION SYSTEM

To maximise engine performance, a sophisticated dual injection system has been introduced. This system features two dedicated injectors: one positioned on the throttle body and one installed directly in the airbox sleeve. This configuration allows for optimal management of the air-fuel mixture, significantly improving response at low revs and ensuring constant power delivery at high revs.

RECONFIGURED DOHC VALVETRAIN

The all-new 250cc engine features a DOHC timing system with overhead camshafts and a chain positioned on the right-hand side rather than the left, driven by a gear linked to the water pump shaft. The timing system uses a Morse-type chain, equipped with a hydraulic tensioner, to ensure maximum reliability even at the high revs delivered by this model.

ELECTRIC STARTER AND LITHIUM BATTERY

Reliable and secure starting on the first attempt in any weather or racing conditions, ensured by the standard electric starter powered by an ultra-lightweight lithium battery.

RACING CRANKSHAFT AND CONNECTING ROD

The internal architecture of the engine reflects the project’s pure racing DNA: the crankshaft features components made from dedicated forged steel and is supported by roller main bearings. The monobloc connecting rod utilises a bushing at the engine head to best withstand the specific high pressures, whilst the piston adopts a robust box-in-box structure.

HANDLEBAR CONTROL AND COMFORT

The handlebar of the RX 250 F is isolated using silent block supports to effectively dampen high-frequency vibrations, reducing arm fatigue during longer riding sessions. For MY27, 5 mm raised handlebar supports have also been adopted to promote a more natural and effective riding position, combined with new grips featuring a softer compound.

DRY SUMMER SYSTEM

Unlike its bigger sister, the RX 250 F’s lubrication system employs a dry sump circuit with dedicated return and delivery pumps. The system uses the same oil, suitably filtered, to lubricate both the engine and the transmission, an engineering choice designed to optimise space whilst ensuring total efficiency under load.

5-SPEED GEARBOX AND HYDRAULIC CLUTCH

The engine is mated to a 5-speed gearbox completely redesigned for this displacement, engineered with geometries and thicknesses that reduce weight and bulk without compromising the mechanical strength of the transmission. The clutch control relies on an updated hydraulic unit derived from the RX 450, capable of ensuring smooth and consistent operation race after race.

CFD-OPTIMISED COOLING


CFD-OPTIMISED COOLING
The engine’s thermal efficiency is ensured by a cooling system developed through in-depth computational fluid dynamics (CFD) analysis. This study enabled the optimisation of internal fluid flow and overall heat exchange, leading to the adoption on the RX 250 F of a closed-type impeller that improves system efficiency and eliminates the need for external piping.

CHASSIS DESIGNED FOR THE MX2 CLASS

The frame has been entirely designed around the specific geometry and stresses of the new 250 4-stroke engine. It features a more tapered lower engine cradle section and dedicated side engine head connections. This configuration increases the vehicle’s overall torsional rigidity, whilst maintaining the optimal vertical flexibility required for intense motocross use.

ENGINEERING AND STYLE:
THE NEW ERA OF MX2

The look of the 2027 Beta RX breaks completely with the past, bringing an aggressive red and black livery to the track that blends perfectly with the black-finished frame and tank. Beneath this aesthetic lies an engineering design focused on maximum mass centralisation: the engine’s incredible compactness and the more tapered lower engine cradle section of the frame not only streamline the bike’s profile but also result in lightning-fast handling and responsiveness through the channels and over jumps.

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manual brochure Tech Specs

CHASSIS

Frame

Molybdenum steel with double cradle split above the exhaust port

Wheelbase

1475 mm

Max length

2170 mm

Max width

830 mm

Max height

1270 mm

Seat height

945 mm

Ground clearance

340 mm

Footrest height

422 mm

Dry weight

101 kg (front 48 kg; rear 53 kg)

Fuel tank capacity

7,0 l

Cooling system capacity

1,3 l

Front suspension

Kayaba Hydraulic USD closecartridge fork with ø 48 mm shaft

Rear suspension

Kayaba Monoshock with progressive compound lever

Shock absorber stroke

133 mm

Front wheel travel

305 mm

Rear wheel travel

300 mm

Front brake

Wave disc ø260 mm and double-piston floating caliper

Rear brake

Wave disc ø240 mm and single-piston floating caliper

Front rim

21 x 1,6 – 36 holes

Rear rim

19 x 2,15 – 36 holes

Front tyre

80/100 – 21

Rear tyre

100/90 – 19

engine

Type

Single cylinder, 4-stroke, liquid-cooled

Bore

78 mm

Stroke

52,3 mm

Displacement

249,8 cc

Compression ratio

14,4:1

Valve train 

DOHC finger-type rocker arms / 4 valves

Starter

Electric starter

Ignition

Mitsuba

Spark plug

NGK LMAR9AI-8

Lubrication

Lubrication 2 oil pumps

Throttle body

Ø 46mm

Clutch

Wet multi-disc clutch

Primary drive

Z. 23/72

Transmission

5 gears

Final transmission

Chain

Engine oil

SAE 10W/50 1l.

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