Honda release details on the new 2021 CRF450RX (and R) – big changes to chassis and engine go deeper than the striking new, all-red colours on Honda’s flagship off-road model.

Very few major components have been spared the attention Honda engineers in developing the 2021 CRF450RX cross-country (and R motocross model). After what the Japanese manufacturer is calling a “comprehensive update” – a lot of which is down to the development of the factory MXGP world championship-winning machine of Tim Gasjer – there’s a lot to pick at.

Underneath the striking new "deep red" colour (not plural) lurks an overall 2.3kg lighter bike, a new frame and swingarm with revised geometry and new Showa suspension which will “greatly improve cornering performance.” The engine gets oval exhaust ports, a single header pipe and muffler exhaust system, a new decompression system (less stalling) and a huge 4.1 litre airbox. And get this…there’s also now a hydraulic clutch plus handguards are standard-fit. Honda, at last!

2021 Honda CRF450RX highlights:

• Dry weight is 107.6kg, 2.3kg lighter than the previous model
• Single header pipe and muffler loses 1.2kg
• New hydraulic clutch with larger plates
• Engine updates including new fuel injector angle, revised throttle body and exhaust ports for increased bottom-end drive and top end power
• 1.8L larger airbox
• Revised decompressor system gives improved stall resistance
• 8mm more ground clearance
• Chassis upgrades include 70mm slimmer overall, 20% less lateral rigidity in the frame, 320g lighter subframe
• A tighter rake and trail (at 27.1°/114mm), more flex in triple clamps, narrower swing arm spars and swingarm pivot point, new swingarm rigidity balance all aid cornering agility
• Re-valved front Showa forks have an extra 5mm stroke
• Larger Showa rear piston valving has faster response and improved bump absorption and new “world’s lightest steel” spring
• New Pro-link suspension link ratio
• Honda’s Selectable Torque Control (HSTC) now sits on left-hand button cluster with HRC Launch Control, Engine Mode Select Button (EMSB)
• HRC Setting tool updated for “Aggressive” and “Smooth” modes
• Improved ergonomics from new smaller seat
• Redesigned plastics have four (was six) bolts to remove side panels
• New single-piece radiator shrouds improve air flow

What’s changed? The 2021 Honda CRF450RX in detail

We’re accustomed to seeing the cross-country spec Honda model based on the 450R motocross sibling (updated in 2017) save for a larger tank, tweaked engine mapping, softer suspension settings and an 18-inch rear wheel.

Since Honda introduced the 450RX model in 2017 development has mirrored the CRF450R with HRC input to increase peak power and torque, launch control, plus revised chassis and brakes in 2019. For model year 2020 Honda in traduced the Selectable Torque Control (HSTC) to boost rider options on the track.

For 2021 the RX is still very much following the MX bike’s lead but we can see some significant development steps in favour, or rather tailored for, off-road and enduro…

Engine refinements

2019 model year was the big boost for the CRF’s 449.7cc, four-valve Unicam engine. Refined PGM-FI fuel mapping, launch control, selectable launch control and more power heralded a new era.

For 21YM the upgrades arrive directly from Tim Gajser’s championship-winning HRC MXGP machine but, with a focus on drivability in the low to mid-range and weight savings aimed at improving rideability and cornering performance, the changes should suit off-road and enduro equally well.

“A significant increase” (up to 0.6kW) in peak power above 5,000rpm is matched by a stronger low-rpm torque feel Honda says of the new engine. It’s the result of a whopping 1.8L larger airbox (4.1L in total volume) on the ‘clean’ side. The new airbox can also now be accessed simply with the removal of one side shroud bolt.

The techy engine bit…

The larger airbox feeds a redesigned, lighter 46mm throttle body which improves intake efficiency and makes active use of latent heat vaporisation in the inlet ports.

The injector angle also moves from 30° to 60°, spraying fuel all the way back to the butterfly to improve intake efficiency, cooling of the charge and all-important throttle feel.

The decompression system is also new: its counterweight is moved from the right of the camshaft to the left, which gives more stable operation at low rpm with increased stall-resistance – something we all like with a big 450 4T.

Single muffler exhaust system

Honda say in fact the biggest change in the engine for MY21 is the twin exhaust ports which, like the CBR1000RR-R Fireblade, have an oval exit rather than round shape for improved efficiency.

Externally the big change is the 2-1-2 design of the previous model exhaust system has been replaced by a single downpipe and muffler (which also does away with a heat shield) saving 1.24kg. The downpipe also tucks in 74mm closer to the centre line (improving rider ergonomics) while the pressed muffler features twin resonators that reduce noise while boosting power.

Hydraulic clutch – at last!

Many Honda riders will be looking at those two words and the image above shouting – “at last!” It’s another update drawn directly from Gajser’s race bike but in truth a hydraulic clutch on a stock CRF450 is overdue.

Honda say it improves both control and feel at the lever (we know this), is 10% lighter to use and delivers consistent lever clearance (biting point) under tough riding conditions. The clutch capacity has also been increased by 27% with an extra plate – from 7 to 8 plates – and works with an extra friction spring to maximise power transmission and durability. Slippage has been reduced by 85% at peak power Honda claims.

Bore and stroke remains 96 x 62.1mm with compression ratio of 13.5:1. A gear position sensor in the five-speed gearbox allows the use of three specific ignition maps for 1st and 2nd, 3rd and 4th, and 5th.

Rock-solid reliability has always been a big factor in the CRF450RX’s success and a 5-hole piston oil jet and dual 12mm drum scavenge pump manage lubrication.

Saving more precious weight is a thinner magnesium cylinder head cover and a smaller fuel pump – it secures with four bolts instead of six, saves 120g and offers the same pressure and filter service life as the previous design.

Chassis changes “elevate” cornering ability

Honda say the 2021 CRF450 has a completely renewed chassis developed with direct input from the HRC race team to “elevate every aspect of cornering ability”.

The details behind that are pretty substantial: narrower main spars weigh 8.4kg, 700g less than the previous design, while the redesigned subframe saves 320g (now 910g). The chassis torsional rigidity is unchanged but lateral rigidity is reduced by 20% to increase corner speed, traction and steering accuracy Honda says. The aluminium swingarm also has a new “rigidity balance” in tune with the new frame with narrower arms and pivot point and the Pro-Link ratio is also revised.

Both top and bottom yokes have more flex, for quicker steering and feel. Fully adjustable, the 49mm Showa USD coil spring fork is a version of the Showa ‘factory’ fork supplied to MX race teams in the Japanese championship.

Smoother cornering performance is promised from the re-valved forks with the stroke lengthened by 5mm to 310mm and the axle clamps’ rigidity increased. The Showa rear shock’s main piston valving is enlarged for faster response and improved bump absorption, plus the spring uses the “world’s lightest steel” to save 200g.

The damping and spring rate of both front and rear suspension are new for 21YM – and lower than the CRF450R – to suit a wider range of conditions and help with comfort over longer rides.

The nerdy chassis bit

If you’re into the numbers Honda say the rake and trail are now a tighter 27.1°/114mm (from 27.4°/116mm) with a 1481mm wheelbase. Ground clearance goes up 8mm to 336mm and the bottom yoke now sits 6.1mm higher at 928mm. The radius arc from swingarm pivot point to rear wheel spindle increases by 0.9°, to 14.5°, while distance between the pivot and front spindle goes up 1.8mm to 914.6mm. Dry weight is 107.6kg, 2.3kg lighter than the previous model. All this, Honda say, further hones cornering ability and rider feel.

Thinking of the rider and mechanic

The new shorter, lighter and 10mm lower (at the rear) seat promises more freedom of movement. Overall the bike is easier to work on with the number of 8mm bolts securing the bodywork dropping from six to four each side.

The new CRF450 is slimmer by 70mm (50mm on the left, 20mm on the exhaust side) with thinner plastics and the tank cover has been removed. The forged aluminium sidestand also now tucks in much closer to minimise interference while riding.

That striking new all-red graphic treatment certainly gives the 21YM CRF450RX’s sharper lines and a whole, new look including handguards as standard at last. Honda say the new handguards add just 222g total – it makes a big difference for us in terms of look but also purpose off-road.

The eight-litre plastic fuel tank has been redesigned to accommodate new Computational Flow Dynamics (CFD) designed radiator shrouds constructed from one-piece plastic, rather than two, that now include a lower vent to improve airflow.

The latest lightweight Renthal Fatbar sits on the new top yoke which features two handlebar positions, adjustable by 26mm either way. When the holder is turned 180°, the handlebar can move an additional 10mm from the base position, resulting in four settings.

Brakes and wheels

The twin-piston brake caliper uses 30 and 27mm diameter pistons biting a 260mm wave-pattern disc with a braided rate brake hose for a strong and consistent braking power. The single-piston rear caliper fits a 240mm wave-pattern disc.

DID aluminium rims, with directly attached spoke pattern layout are finished in black and Honda say the rear wheel is both stronger and lighter for 21YM with Dunlop’s enduro-ready Geomax AT81F/AT81 tyres in 90/90-21 front and 120/90-18 rear sizes.

Electronic aids as standard

The CRF450RX gained selectable torque control (HSTC) in model year 2020 and the system is unchanged for 21YM. It basically minimises rear wheel spin and naturally helps with traction in tougher conditions not by a wheel speed sensor but via “feel” at the throttle while managing power; ignition timing is retarded and the PGM-FI controlled when the rpm rate change is detected to have gone over a set amount.

Three HSTC modes for different riding conditions:

Mode 1 intervenes lightly and after the longest time – useful for reducing wheelspin and maintaining control in tight corners.

Mode 3 intervenes more quickly, more strongly and is useful in more slippery, muddy conditions.

Mode 2 naturally offers a mid-point between 1 and 3 in terms of speed and strength of intervention.

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

An obvious update for 21YM is the rider controls and display switchgear on the left side of the handlebars. The Launch Control indicator, EFI warning, EMSB mode button, LED indicator and HSTC button are now all incorporated on one side (shown above).

Launch time

HRC Launch Control gives riders the best option for a race start and also has 3 modes to choose from:

Level 3 – 8,250rpm, muddy conditions/novice

Level 2 – 8,500rpm, dry conditions/standard

Level 1 – 9,500rpm, dry conditions/expert

Engine mode options

The Engine Mode Select Button (EMSB) alters the engine’s characteristics and three maps are available to suit riding conditions or rider preference:

Mode 1 – Standard

Mode 2 – Smooth

Mode 3 – Aggressive

(LED also displays mode selected, but with a blue light).

A  mapping update in the HRC Setting Tool for 2021 models also allows a “Smooth” mode, with gentler throttle response for novice riders or an “Aggressive” mode with a hyper-sensitive throttle reaction and engine response for race conditions.

2021 Honda CRF450RX Technical Specifications:

More information including pricing and availability:

Honda.co.uk

Honda North America

Honda Australia