27YM Honda CRF450RX

Quick summary: More power, less weight, sharper handling and increased style – the 27YM CRF450RX is effectively a brand-new machine that moves the game on again

New Model: Honda’s ultimate cross-country machine soars forward in one giant leap. Sharing the extensive updates of the 27YM CRF450R, including for the first time its Titanium fuel tank, the 27YM CRF450RX is effectively a brand-new machine. Its all-new 449.5cc engine boasts a bigger bore, shorter stoke and larger diameter inlet and exhaust valves, plus new piston and crankshaft as well as a higher compression ratio. Power is up 10%, torque 4%. A more compact gearbox houses revised ratios to make use of the performance upgrade while an innovative new clutch design incorporates slipper action. The starter system is also smaller in size. The electronics package – HRC Launch Control, HSTC and EMSB – has been completely refreshed to equal the new, increased output. Overall, 5.6kg mass has been shaved; the twin-spar aluminium frame is 70% new and matched to a totally revised, longer aluminium swingarm. New chassis geometry moves weight rearward with cornering control and stability increased by updates to RX-specific Showa suspension and Pro-Link to provide consistent, smooth reaction in each part of the stroke. New bodywork aids rider movement and, as in 26YM, hand guards, side stand and an 18in rear wheel are standard fit while a new, larger bash plate protects the underside. And, for 27YM, HRC’s Tricolour graphic makes its stunning off-road debut.

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Contents:

1. Introduction
2. Model overview
3. Key features
4. Technical specifications  

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1. Introduction

For 17YM Honda introduced an all-new, competition-ready cross-country machine into its off-road line up – the CRF450RX. And it took as its rock-solid base the engine and chassis of the 17YM CRF450R – Honda’s first totally new 450cc motocrosser in eight years – with modifications including larger fuel tank,18-inch rear wheel, revised PGM-FI mapping and suspension changes. 

The CRF450R was the perfect platform to expand on and gave the CRF450RX both the pure MX DNA to deal with any special stage and the confidence-inspiring competence to handle flat-out trails, challenging climbs and tight, tricky sections. And, just as importantly to an owner, it’s a high-quality machine built with the long-term Honda reliability that makes it easy to live with over years of use.

An HRC-developed cylinder head upped peak power and torque considerably in 19YM; HRC launch control was also added along with revised rigidity balance for the frame and swingarm, a new front brake caliper and adjustable-position Renthal Fatbar. For 20YM, just like its MX sibling, it received Honda Selectable Torque Control (HSTC).

21YM saw a major upgrade for the CRF450RX and it started out from the exact same point as the CRF450R, which was almost totally redesigned by HRC. 22YM garnered ECU settings and suspension updates, with more torque and chassis upgrades in 23YM. Development has always gone hand in hand with the needs of HRC’s factory riders and the 25YM CRF450RX aimed at making going fast easier on a rough track, adding upgraded stability and braking to its turning performance.

For 27YM evolution has been set aside for revolution. And while it builds on the strengths of the previous model, the CRF450RX now loads a brand new, much more powerful engine with redesigned chassis to match and completely revised suspension philosophy. Every detail of which has been gathered through the course of world-class competition. As ever it’s an off-road tool designed to make going faster easier – and for longer.

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2. Model Overview 

Every update to the CRF450R is focused on delivering a clearer competitive edge, and the headline numbers reflect that immediately: 10% more power, and 4% more torque. And, without fuel, at 103.5kg a huge 5.6kg lighter. The result is a machine that accelerates harder, responds faster, and feels noticeably lighter and more agile on track.

That performance gain starts with a more efficient, harder-revving engine. The redesigned, more compact unit features a larger bore, a new piston with revised crown, and an all-new crankshaft that enables a shorter stroke and higher compression ratio. Larger titanium intake valves join newly introduced titanium exhaust valves, while a reworked UNICAM valve train improves gas flow efficiency, helping the engine breathe better and deliver stronger, more usable power.

Drive out of corners is further improved through a more compact transmission with revised gear ratios, increasing rear wheel thrust across a wider speed range to allow riders to apply power earlier and with greater confidence. The clutch introduces a world-first rubber damper-activated Back Torque Limiter (BTL), bringing refined slipper performance validated by HRC in MXGP, while a redesigned starter motor saves both weight and space.

Control is just as important as outright performance, and the electronics package reflects that. HRC Launch Control and Honda Selectable Torque Control (HSTC) are now updated with settings taken directly from factory race machines, offering sharper, more adaptable performance in changing conditions. The Engine Mode Select Button (EMSB) continues to give riders instant control over engine character, tailoring delivery to suit both rider preference and track demands.

Handling has been sharpened, stability increased, and predictability across even the roughest of track conditions improved by a 70% new frame. It features revised steering geometry, placing more weight rearward, with an 11.6% lighter – and all new – aluminium swingarm. A refreshed direction for the Showa suspension (front and rear) applies appropriate friction in areas while building smooth, consistent reaction and control in every part of the stroke. All settings are exclusive to the RX. A revised Pro-Link linkage contributes to this upgraded performance, as does an all-new (and more rigid) rear wheel and hub. Tyres are Dunlop AT81s.

For the first time the CRF450RX shares the slimline 7.1L Titanium fuel tank of its MX sibling. The radiator shrouds and rear side covers feature deeper radius cutouts to aid cornering and acceleration, with a new seat contour to match. The bash plate too is now much more protective. Recycled material has also been employed for most of the bodywork’s construction. And linking Honda’s off-road racing to MotoGP and WSBK HRC’s famous Tricolour colour way makes a sensational mark on the 27YM CRF450RX’s graphic treatment.

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3. Key Features
    3.1 Engine 

• Revised specification represents biggest change to the CRF’s powertrain in over a decade
• New design 10% more powerful with 4% more torque across the rev-range
• 2.7kg lighter plus 17mm reduction in width
• Bigger bore, shorter stroke, larger intake/exhaust valves and new UNICAM valve train
• Redesigned piston, increased compression ratio plus new, more rigid and efficient crankshaft
• Updated intake increases airflow; new exhaust is lighter and conforms to AMA/FIM 111dB regulations.
• RX-specific ECU settings smooth output
• New, more compact transmission uses revised ratios to match performance boost
• New clutch smaller, lighter and with HRC-developed rubber damper activated Back Torque Limiter (BTL) slipper action is a world’s first application
• Starter unit new, rationalised to save weight and space

27YM sees a huge update for the CRF450R’s engine in terms of physical size, weight and performance. It’s effectively brand new, more compact, and much lighter. And much more powerful, just over 10.3% at peak – at higher rpm – with 3.7% more peak torque. Bore size has increased 1mm to 97mm over the 26YM design, allowing the use of larger diameter valves – 40mm inlet and 32mm exhaust (as opposed to 38/31mm). Stroke is now set at 60.83mm, from 62.1mm. 

A redesigned airbox simplifies and straightens the airflow path into the engine, minimising resistance. The 27YM design also loses the lid of the 26YM design. An air filter with revised  density plus a more rounded shape has the same surface area as before but reduces airflow resistance by 10%. New ECU settings provide optimum response and control.

The intake port is also steeper, by 5°, and 10mm shorter while an optimised valve angle further boosts the downdraft intake efficiency, improving both output and drivability – core strengths of the engine. As before, the compact UNICAM single camshaft design offers the wide valve-timing flexibility enabled by finger-follower rocker arms. More aggressive cam profiles are driven by a new, higher rigidity and lighter weight valvetrain with intake and exhaust rocker arm shafts aligned on a common axis.

A new piston crown shape and optimised combustion chamber profile enhance combustion efficiency, and ups compression ratio from 13.5:1 to 13.75:1. A Diamond Like Coating (DLC) has also been applied to the top piston ring, reducing friction and producing more consistently stable operation with superior reliability.

The 26YM engine employed an ‘anchor’ shaped crank web profile; for 27YM a ‘round’ profile replaces it, increasing overall crankshaft rigidity. New journal roller bearings (as opposed to a ball/roller combination) reduce deformation from combustion pressure, converting it more efficiently into rotational energy with reduced friction at bearing and gear engagement points.

The exhaust conforms to AMA/FIM sound regulations (111dB) and is optimised for performance. The new muffler is longer but lighter, 2.76kg rather than 2.91kg. Also, longer is the downpipe, despite it too shaving 53g over the previous design weighing 1.111kg.

Drawn directly from HRC feedback to optimise inertia and controllability, the clutch is an all-new design, 7mm smaller in diameter at 132mm and 400g lighter. The unified steel construction of the previous primary drive gear has been replaced with a ring-shaped gear, minimising the amount of steel required. 

In addition to the conventional clutch rubber function of absorbing and mitigating torque fluctuations, and in a world’s first application, a rubber damper-activated Back Torque Limiter (BTL) adjusts clutch capacity through deformation of the damper as back torque is generated, and acts with a ‘slipper’ function, greatly reducing the rider’s clutch load and improving overall engine manageability. Optimal shaping, structure, durability and limiter-capacity settings were all tested throughout real time MXGP competition.

In the transmission, the main shaft bearing annular collars have been replaced with split resin cage needle bearings, allowing each gear to be optimised for shape, shaft diameter, wall thickness and positioning without being restricted by adjacent gear geometry. As a result, overall transmission width has been reduced through utilisation of a 14mm shorter transmission shaft, which also nets a 509g weight saving. 

The shift drum itself is also 134g lighter than before and, at 63.5mm, 13.4mm shorter in length. The weight reduction has been achieved by using a higher-tensile material for its construction, which allowed for the drum to have thinner walls. The smaller size has been achieved by reducing the shift drum’s lead grooves from 3 to 2. 

To match the boost in engine output, revised gear ratios and 51 tooth final drive sprocket (increased by 2 teeth) deliver much more driving force, across a wider speed range.

Also redesigned – and 500g lighter – the starter system now operates through a 4-axis configuration (down from 5) and uses a lightweight friction-disc torque limiter rather than a press-fit design. The starter one-way clutch is smaller in size with a lighter weight outer structure.

The new lighter and more compact transmission, clutch and starter have allowed optimisation of the surrounding components; net result is a 17mm reduction in engine width and a 2.7kg mass saving compared to the previous design.

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3.2 Electronics

• HRC Launch Control updated with settings from the factory bikes
• Honda Selectable Torque Control (HSTC) also optimised for upgraded engine performance
• Engine Mode Select Button (EMSB) features 3 maps to adjust output character 

HRC Launch Control has been tuned to match the increased engine output, with new settings drawn from the factory competition bikes. As before there are three modes, and each ‘waiting’ rev limit offers good start potential with maximum drive/minimum wheelspin. After starting, the rev limit returns to normal

• Mode 1: High waiting rpm, then returns to normal immediately
• Mode 2: Slightly lower rpm than Mode 1, returning to normal immediately
• Mode 3: Low waiting rpm and gradually returns to normal in a few seconds. 

HRC Launch Control can also be switched off completely. 

The HSTC works to minimise rear wheel spin (thus reducing wasted forward drive) and maximise traction. It doesn’t use a wheel speed sensor and critically maintains feel at the throttle while managing power; ignition timing is retarded and the PGM-FI controlled when the rate of change of rpm is detected to have gone over a set amount.

Three modes differ in drive management level for different riding conditions:

• Mode 1: Intervenes most lightly, and after the longest time ­– offering high wheelspin
• Mode 2: Naturally offers a mid-point between 1 and 3 in terms of speed and strength of intervention and maintaining control in tight corners
• Mode 3: Has the system intervene more quickly and strongly, with low wheelspin, and is therefore useful in more slippery, muddy conditions.

HSTC can also be switched off completely. When the engine is turned on, the system uses the last-selected setting.

There are also three modes available via the Engine Mode Select Button (EMSB) to alter engine character. Mode 1 is the factory setting, 2 smooth and 3 aggressive.

The Launch Control indicator, EFI warning, HSTC and EMSB mode button, and LED indicator are sited on the left handlebar. Pressing and holding the HSTC button for 0.5s will cycle the system to the next mode, with a green LED indication – 1 blink for Mode 1, 2 for Mode 2 and 3 for Mode 3 – to confirm selection.

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3.3 Chassis

• 70% new mainframe with revised steering geometry to increase rear drive and cornering traction
• Kerb weight of 108.8kg, 6.4kg lighter
• Brand new aluminium swingarm 11.6% lighter
• Completely revised suspension front and rear builds smooth, consistent control everywhere in its stroke, with dedicated RX off-road settings
• New Pro-Link linkage smooths corner exit
• New 18in rear wheel and axle feature increased rigidity for improved drive

Built around the goal of boosting stability, cornering performance, rear drive and overall traction, the new chassis’ base dimensions and rider position have been revised for 27YM. Wheelbase increases from 1482mm to 1490mm, with rake going from 27.3° to 27.5° and trail 115.3 to 116.7mm. The footpegs move 5mm rearward, and the rear axle downward offset decreases, whilst weight distribution moves slightly forward for a more balanced split.

Overall, the new CRF450RX is considerably lighter, with a fuel-free mass of 103.5kg and ready-to-go kerb weight of 108.8kg (from 109.1kg/115.2kg).

The twin-spar aluminium main frame features a 70% redesign, with the aim of enhanced stability and predictability on the roughest of track conditions. Up front, the head pipe – adjusted for the new rake angle with an upsized cast, rather than forged gusset – down tube and front joint are optimised for rigidity and weight. As a result, longitudinal and torsional rigidity of this area increases 10%, with zero increase in weight over the 26YM model.

Also optimised for rigidity and shape are the swingarm pivot plates, shock absorber upper bracket and subframe mounting brackets. The cylinder head hanger plates – now constructed of aluminium instead of steel – are 152g lighter. As the engine is now more compact, revised lower down tubes and middle hanger brackets have been applied. The rear subframe employs a simplified design, making space for easier air filter maintenance.

The smoothly blended weld design between the cross-member and main pipe creates a more continuous structure, allowing the use of larger-diameter, thinner-wall tubing for improved stiffness and lower weight; ultimately saving 415g in total. Each spar is now a smooth D-shape in cross section, improving rut riding ability. For 27YM, the swingarm is now marginally longer than before. On an aesthetic level, for the first time in 7 years the look of the swingarm’s twin main spars has been refreshed. The smooth, step-free design is meticulously hand polished into hairline finish, and utilizes evenly patterned fish scale weld for a premium finish. 

Upper/lower reinforcement of the chain slider and addition of a damping hole improves drive, while the guide plate structure uses Dakar-derived technology and a high-impact resistant resin material, reducing deformation under impact loads.

To reduce ‘kickback’ and improve ride comfort and stability under acceleration, the Pro-Link linkage ratio has been adjusted. Thrust needle bearings have also been adopted (replacing thrust washers) in the link arm, enhancing smoothness with improved feel for traction.

The development aim of the 27YM machine’s Showa suspension was to build on the success of the 26YM design, with reduced front/rear pitching under acceleration/braking, and improved stability. And, in fact, to grow a real advantage as track conditions get tougher. 

Also, the philosophy has changed from the 26YM machine. Before ‘low friction’ was the over-riding target; for 27YM this has changed, with a considered amount of friction added to the suspension stroke, from the initial movement. This has been achieved by completely upgrading the 49mm USD forks, with the main damping force now coming from a Dynamic Blow System (DBS) piston; this change increases compression damping in the extremely low to low-speed range, improving stroke consistency. Compression and rebound damping at both ends have been increased without introducing any harsh, or negative characteristics. Specialised RX settings make the suspension off-road ready, suitable for the varied terrain away from the MX track.

Contributing to this new performance is a reduced diameter hole on the main piston rod, as well as reduced thickness of the SUBCOMP valve shims – plus more of them. Stiffer main springs (5.2N/mm up from 5.0N/mm) also create a firmer front-end feel, and the spring seat moves from conical resin to aluminium cylinder. 

Further elevating smooth control with consistency factory-spec, Kashima coating has been applied to the rod and cylinder. As a visual clue to the premium upgrade, the fork cap sub tank also receives Kashima coating. 

A fine detail – but very much an HRC update – is application of a dedicated seal for the steering stem resulting in careful friction management of the steering characteristics, adding to the chassis’ overall improvement in stability.

The 50mm single tube rear shock too has been redrawn; 40g has been shaved by careful internal machining of the damper casing underscoring the granular level upgrades Honda engineers have undertaken with the 27YM CRF450R. This is paired with an increased piston oscillation range and revised bump stop, which allows for a wider operating window for the damper stroke, increasing stability and improving the rear wheel contact patch, ultimately improving traction. 

And, taken directly from HRC’s factory bikes and re-engineered for mass production, the shock upper mount now uses an oscillation-limiting structure. This design limits shock ‘play’ while moderating initial impact harshness, resulting in upgraded overall performance. The coil spring guide of the compression adjuster has also been redesigned to optimise adjustment sensitivity.

Knuckle guards protect hands and levers while the forged aluminium sidestand tucks away neatly to minimise interference while riding. Drawn from parts employed by HRC’s bikes the two-piston front brake caliper uses pistons and piston seal grooves that reduce lever play when caliper temperature is high. The caliper itself reduces rigidity change when hot, improving brake lever linearity and reducing rider fatigue. The 260mm wave-pattern disc is unchanged; a single-piston rear caliper is matched to a 240mm wave-pattern disc.

DID aluminium rims, with a directly attached spoke pattern layout are finished in black; the front is a 21 x 1.6in, while the rear 18 x 2.15in wheel is an all-new design created with feedback from the HRC Factory bikes for a 270g weight reduction, increased strength, improved serviceability and enhanced riding performance.

An increased bearing span of the rear wheel hub increases wheel rigidity and reduces axle deformation, while an updated spoke diameter and revised lacing pattern increases traction, optimises roll direction rigidity and extends spoke life. A stronger rear drive sprocket is result of an increase in mounting diameter – from 153 to 160mm. Upgraded to a fully machined part the 51-tooth sprocket also features a redesigned lightening hole pattern.

Dunlop’s bespoke enduro-ready AT81 Geomax tyres are fitted as standard equipment.

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3.4 Styling

• New, slimmer 7.1L Titanium fuel tank shared with the CRF450R
• Redesigned radiator shrouds and side covers incorporate deeper radius cutouts to aid cornering and acceleration. 
• Handguards and side stand standard fit; 27YM bash plate much more protective
• Simplification of maintenance throughout the bike
• New graphics incorporate HRC’s Tricolour, linking Honda’s racing activities across off-road, WSBK and MotoGP
• Sustainable recycled materials used for bodywork manufacture

Overhauled for 27YM, the CRF450R loads with new dynamic bodywork and livery. The shrouds and side covers have been updated to facilitate a flat knee trajectory, front to back of the machine, and the side covers are now symmetrical in shape, improving the rider’s gripping power when the rear is fully loaded under acceleration. The seat contours have changed to match, with a smaller radius at the rear, and height now down 953mm (down from 957mm). 

The 26YM CRF450RX used a plastic 8L fuel tank. For 27YM it now shares the 7.1L Titanium fuel tank of the CRF450R; while it holds .9L less fuel, it’s considerably slimmer – 374mm wide shroud-to-shroud – as opposed to 409mm. Also redesigned for maximum protection and light weight is a much larger bash plate.

Up front, the shroud front corners have been made larger in radius to improve lateral movement while cornering seated. Many areas of access have been simplified, for easy maintenance. New graphics – merging the HRC Tricolour and Big HONDA logo – unify the Honda Racing brand across on and off-road.

And, as part of Honda’s aim for zero environmental impact by 2050, the front mudguard, number board and radiator shrouds are constructed using Post Industrial Recycling (PIR) material. Made up of a special selection of highly transparent recycled raw materials PIR delivers high weather resistance and high gloss finish. The seat base, too, is made from high impact PIR.

Standard-fit, lightweight Renthal Fatbar flex for optimal comfort; the top yoke features two handlebar-holder locations for moving the handlebar rearward and forward by 26mm. When the holder is turned 180°, the handlebar can be moved an additional 10mm from the base position, resulting in four unique riding positions.

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4. Technical Specifications 

All specifications are provisional and subject to change without notice.

# Please note that the figures provided are results obtained by Honda under standardised testing conditions prescribed by WMTC. Tests are conducted on a rolling road using a standard version of the vehicle with only one rider and no additional optional equipment. Actual fuel consumption may vary depending on how you ride, how you maintain your vehicle, weather, road conditions, tire pressure, installation of accessories, cargo, rider and passenger weight, and other factors. 

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