Beta RX 450 and RX 300 2025 Review

It was a bold move for a brand cemented in trials and enduro, but Beta entered the four-stroke motocross market last year with the 2024 RX 450 after a couple of years racing and testing prototype versions in the MXGP Championship. The 450cc motocross segment is as fast as it is furious, but Beta has not shied away from the task at hand and has updated the 2025 model with some subtle but notable changes. 

Starting from the top, the handlebar clamps are new and feature anti-vibration properties thanks to what Beta calls silent blocks. This does raise the handlebar height by 5mm but it’s a sweet feature. So sweet, in fact, the silent blocks are fitted to all 2025 Beta motocross and enduro models.

The structure of the sub-frame and air-filter housing has been reinforced to strengthen and stiffen this region of the bike. The KYB fork and shock have been recalibrated to enhance stability, a new lithium battery features more amps, the engine mapping has been updated, and the rear sprocket has an additional tooth making it a 51-tooth cog.

The footpegs are new and less bulky than the previous model, the rear wheel axle has been beefed up and is 2mm bigger in diameter to increase stiffness, and there’s no chain adjuster blocks and new adjuster bolts with a larger 10mm thread. Finally, there is a new look with fresh graphics.

There may not be anything ground-breaking with the updates to the 2025 Beta RX 450 but this bike packs quite a surprise out on the track.

450 delight 

For those who are not up to speed with the Beta RX 450, this bike is as serious as any other player in the 450cc motocross bike segment. Equipped with a KYB fork and shock, HGS exhaust header and silencer, five-speed transmission, sleek bodywork, handlebar-mounted mapping switch with a dry or wet map plus traction control and four different throttle tube cams to customize the throttle pull, this bike is ready for racing straight from the showroom floor.

Benny Bloss has been racing the RX 450 in AMA Monster Energy Supercross while Ben Watson and Ivo Monticelli have been throwing down in MXGP on the red rocket. Big results may have eluded them to date but when you look at the rider talent signed to most of the competition you can understand the task at hand. So, what is the Beta RX 450 really like?

This bike is a pleasure to ride. There’s plenty of 450cc four-stroke power but it’s just so easy to use. It may not feel like a fast bike but this is a bike you can ride fast. The combination of smooth power delivery and KYB suspension that is tuned for the average rider combine to deliver a machine that can be ridden with confidence. 

The RX turns with ease and corners with confidence. I couldn’t wipe the smile from my face. Far from a hard-hitting and aggressive nature, the RX is more like a silent assassin that possesses the right mix of potency to win. 

RX 300 smokeshow

The 2025 RX 300 is all-new. This model was previously an enduro model in disguise which wasn’t necessarily a bad thing, but what Beta has done to this bike for 2025 is make a motocross-specific machine. The RX 300 has a new frame with a 10mm wider spar and redesigned and reinforced section in comparison to the enduro models. The new frame was designed to cope with the increased speeds and impacts of motocross making it more stable. The aluminium sub-frame is new, as is the air-filter housing. 

The KYB fork has increased travel and new valving while a new 50mm KYB shock completes the suspension package. The Nissin front brake caliper is new and is the same as what’s fitted to the RX 450 while the rear brake master cylinder is the same as what’s is fitted to the RR Race enduro models. The RX 300 has new radiators, a new 49-tooth rear sprocket which is up a tooth from the previous model and it has a new non O-ring chain.

What’s really big news with the RX 300 is the engine, which is totally new and features a new cylinder, cylinder head and modified intake crank cases. The transmission is all new and is now five-speed making it specific to motocross use. New mapping mates up with the new jetting for the Keihin PWK38 carburettor and adjusted power valve along with a new HGS exhaust.

Like the RX 450, the RX 300 smoker also has new graphics, new silent handlebar clamps, new footpegs, new rear axle and chain adjuster blocks and adjuster bolt threads. 

If you think you know what a Beta 300 two-stroke is like because you’ve ridden a RR 300 or even a Race model, think again. This thing is a pure-bred MX animal. It barks and it bites. The RR 300 enduro models have a bore and stroke of 73 × 69.9mm as opposed to the RX with 72 x 72mm, boosting the RX to 293.1cc over the RR 292.6cc. The RX also features a bigger carburettor with a Keihin PWK38 while the RR runs a PWK36.

In stock trim this bike likes to be revved and when you give it the berries – it goes! The RX 300 requires an aggressive style of riding to keep it on song and when you do, you are handsomely rewarded. This bike would be a real class contender in events like the Hattah Desert Race. 

Riders that prefer a smoother power delivery can take advantage of the easily adjustable power valve and the power valve spring is also easily changed. This is a simple and very effective tuning tool. The dual-map feature really works but not as well as it does on the RX 450. The power delivery is a bit fluffy and rich in the rain map and I found it performed better in the sun map. This bike rips and revs out hard in each gear. If you want to spin your wig, get a test ride on the RX 300. 

SPECS: BETA RX 450

ENGINE
Engine type: Liquid-cooled four-stroke 
Capacity: 449.3cc
Bore x stroke: 97 × 60.8mm
Compression ratio: 13.5:1
Fuel system: EFI
Start: Electric

TRANSMISSION
Type: 5-speed
Final drive: Chain

CHASSIS AND RUNNING GEAR
Frame: Molybdenum steel 
Front suspension: 48mm KYB Closed Cartridge 
Rear suspension: KYB
Front brake: Hydraulic Nissin single disc
Rear brake: Hydraulic Nissin single disc

DIMENSIONS
Claimed dry weight: 104.5
Overall length: 2170mm
Seat height: 945mm
Wheelbase: 1485mm
Ground Clearance: 335mm
Fuel tank capacity: 7-liters

OTHER STUFF
Price: $15,295 plus dealer delivery
Colours: Red
Bike supplied by: betamotor.com.au