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As with the CRF450R, all parts of the 2021 version of the CRF450RX are new, with the exception of the wheels and the motor. The comprehensive update benefits directly from the know-how that HRC was able to gather through the development of Tim Gajser's factory machine, with which he drove to the Motocross World Championship in 2019. The new machine is 2,7 kg lighter and comes with a new frame and swingarm, as well as changes to the geometry and suspension that significantly improve cornering behavior. The engine receives improvements to the intake and exhaust system, a new decompression system and a single muffler - together this leads to a smoother response and improved drivability in the lower and middle speed range. A larger hydraulic clutch provides more control with less leverage. More compact plastic parts and a smaller bench increase freedom of movement. Hand protectors are now standard and an improved layout of the side stand improves driver ergonomics.
2021 Honda CRF450RX Enduro
With the CRF450RX, Honda introduced a completely new competition enduro in 2017. The engine and chassis of the CRF450R from the same year served as the basis, Honda's first newly developed 450 cc motocross model since 2009. The modifications for the RX included a larger fuel tank, an 18-inch rear wheel, a revised PGM-FI Mapping as well as changes to the suspension. The CRF450R was the ideal basis for the CRF450RX: With its motocross DNA, it has the ideal prerequisites for fast enduro sections, but also the necessary confidence for flat trails, demanding climbs and narrow, tricky passages.
CRF450R and CRF450RX further developed
In terms of further development, the CRF450R and the CRF450RX also followed the same path: A cylinder head newly developed by HRC significantly increased peak output and torque in 2019. Further updates were the launch control from HRC as well as a revised stiffness balance for the frame and swingarm, a new brake caliper at the front and a fat bar handlebar from Renthal with adjustable mounts. In 2020, the Honda traction control (HSTC) was added. In 2021 the next significant evolution of the CRF450RX will come. Like the new CRF450R (which was almost completely redeveloped based on Tim Gajser's motocross world champion bike), the RX version is also an extremely impressive, extremely fast off-road machine that is characterized by its high quality and reliability. It was built to serve the driver well for years.
Model overview
The aim of the improvements for both 2021 models was to build the “ultimate weapon” for off-road competition use. The CRF45RX is 2,3 kg lighter thanks to revisions to the frame and subframe. Thanks to the rigidity balance of the new frame and the new swing arm, combined with a tighter chassis geometry, more ground clearance and changes to the suspension, optimum cornering behavior is achieved.
The engine also benefits from HRC's know-how: it now places a strong focus on torque in the lower to medium speed range. The decompression unit was relocated, the volume of the airbox increased, the throttle valve housing revised and the outlet openings re-shaped. The exhaust manifold is also new, and a single silencer replaces the previous twin silencers.
There is also an enlarged hydraulic clutch including reduced manual force and other weight-saving details such as a smaller fuel pump and an optimized cylinder head cover made of magnesium. The new plastic parts are also lighter and slimmer to support the driver's freedom of movement. The bench has also been changed, it is now smaller and shaped lower at the back. In addition, hand guards are now standard and the layout of the side stand has been optimized. An attractive new graphic design - completely in red - completes this comprehensive model update.
the new chassis
- Narrower tubes and swing arm pivot point on the rear swing arm, including revised swing arm stiffness balance
- Geometry changes in combination with the changes mentioned above improve the turning behavior
- Front fork with new damping valves and 5 mm more suspension travel, combined with a rear shock absorber that also works with new damping valves
- Improved ergonomics thanks to a smaller, new bench and more compact, newly designed plastic parts
The CRF450RX's double-loop aluminum frame remained unchanged on the 2020 model. For the 2021 season, it has now been completely renewed with direct input from the HRC racing team in order to improve every aspect of cornering behavior.
Thanks to the narrower tubes, the main frame, at 8,4 kg, now weighs 700 g less than its predecessor, while a newly designed subframe, now weighing 910 g, also saves 320 g. The chassis dynamics are also new: while the torsional rigidity is retained, the lateral rigidity has been reduced by 20% in order to increase cornering speed, traction and steering accuracy. The aluminum swing arm has a new rigidity balance that is tailored to the frame with narrower tubes and pivot point. The pro-link ratio has also been revised.
Both the upper and lower triple clamps have been redesigned. They now offer more flex for faster steering and a better steering feel. The fully adjustable 49mm Showa USD suspension fork is a variant of the Showa “factory” fork supplied to MX racing teams in the Japanese championship. The forks were redesigned with the aim of improving, smoother cornering behavior: the spring travel increased by 5 mm to 310 mm and the stiffness of the axle clamps was increased. The main piston valve on the Showa rear shock absorber has been enlarged for faster response and improved shock absorption. Its spring also uses the lightest steel in the world - this saves another 200 g in weight.
The front and rear damping setting and spring rates have been changed on the 2021 model and are lower than those of the CRF450R. This increases the range of use of the CRF450RX and ensures better comfort on longer journeys.
The seat is now shorter, lighter and 10 mm lower at the rear to support the driver's freedom of movement. It is also much easier to remove and install. Maintenance has also been simplified as the number of 8mm screws securing the bodywork has been reduced from 6 to 4 per side. The new machine is also 70 mm slimmer (50 mm on the left side, 20 mm on the exhaust side) and the plastic parts are thinner, and the tank cover has been saved.
The values for steering head angle and caster are now lower at 27,1 ° and 114 mm (previously 27,4 ° / 116mm) and the wheelbase is 1481mm. Ground clearance increases by 8mm to 336mm, and the lower triple clamp is now 6,1mm higher at 928mm. The radius from the pivot point of the swing arm to the rear wheel axle holder increases by 0,9 ° to 14,5 °, while the distance between the pivot point and the front axle holder increases by 1,8 mm to 914,6 mm. The dry weight is 107,6 kg, which is 2,7 kg lighter than the previous model.
Designed with Computational Flow Dynamics (CFD) technology for maximum air flow, the radiator shrouds are made from one instead of two plastic parts and have a lower vent, while the radiator grilles are optimized for airflow. The 6,3 liter titanium fuel tank has also been improved.
A light Fatbar-Flex handlebar from Renthal is standard for optimal comfort. The upper triple clamp has two handlebar brackets that can be used to move the handlebars back and forth by 26 mm. If the holder is rotated 180 °, the handlebar can be moved a further 10 mm from the basic position, resulting in four individual driving positions. When it comes to weight savings, many smaller amounts also lead to success (“A mountain can form from enough dust”, as a Japanese proverb says); In this sense, the machine's cabling, which has now been optimized again, saves a further 100 g.
New protectors on the handlebars protect hands and fittings and weigh only 222 grams. The forged aluminum side stand has been redesigned. In order to minimize disruptive influences while driving, it is now much closer to the frame.
A double-piston brake caliper with 30 and 27 mm piston diameters and a 260 mm wave disc is used at the front. Together with the brake hose with a low expansion rate, the system offers both an optimal pressure point and maximum stability. The rear single-piston brake caliper works in conjunction with a 240 mm wave disc.
The DID aluminum rims are painted black; the front wheel rim is 21 x 1,6 inches and the rear wheel rim is 18 x 2,15 inches. The rear wheel on the 2021 model is both stronger and lighter. Dunlop Geomax AT81F / AT81 Enduro tires are fitted as standard.
A striking, new and completely red graphic concept underlines the now even sharper lines of the 2021 CRF450RX.
Engine of the 2021 Honda CRF450RX Enduro
- Larger airbox plus redesigned throttle body and exhaust ports for more power in the lower speed range
- New exhaust manifold and new individual silencer increase torque and save weight
- An enlarged, hydraulic clutch replaces the cable actuation and ensures smooth operation and little manual effort
- Revised decompression system reduces the risk of death
After a power increase of 1,8 kW at its peak, plus 2 Nm more torque and more power in the lower speed range in the 2019 model, the further development of the 449,7 cc four-valve Unicam engine for 2020 concentrated on optimizing the PGM-FI -Mappings and the HRC Launch Control as well as the integration of the new traction control Honda Selectable Torque Control (HSTC). With the new machine for 2021, the focus is on upgrades that are directly derived from Tim Gajser's HRC world champion machine: They bring significant improvements in drivability in the lower to medium speed range as well as weight savings to further improve cornering performance.
A significant increase (up to 0,6 kW) in peak power above 5.000 rpm is accompanied by a more noticeable torque at low engine speeds, which is the result of an airbox that has been increased by 1,8 l to 4,1 l. This is now easily accessible by removing a side panel screw and feeds a newly designed, lighter 46 mm throttle body. It optimizes the efficiency in the intake tract and actively uses the latent heat of vaporization that arises in the intake ducts.
The injection nozzle angle was increased from 30 ° to 60 °, which means that the fuel is sprayed in the opposite direction to the intake air in the direction of the throttle valve. This improves the intake efficiency, the cooling of the mixture and the important "throttle valve feeling" for the driver. The decompression system is also new: its counterweight is shifted from the right side of the camshaft to the left, which results in more stable operation at low engine speeds with less risk of death.
The biggest change concerns the dual exhaust ports: like the CBR1000RR-R Fireblade, its exit is oval instead of round to improve its efficiency. The 5,08 kg 2-1-2 exhaust system of the previous model has now been replaced by a single, only 3,84 kg system of manifold and silencer (which also eliminates a heat shield), which saves a total of 1,24 kg. The manifold is also mounted 74mm closer to the central axis (which improves driver ergonomics), while the muffler is equipped with double resonators that both reduce noise and increase performance.
An innovation that was derived directly from Gajser's World Championship motorcycle is the installation of a hydraulic clutch. This improves both control and the feel of the lever (it works 10% lighter) and ensures an even lever spacing under difficult driving conditions. The clutch capacity has been increased by 7% with an additional disc (from 8 to 27 discs) and works with an additional spring to maximize power transmission and durability. The slip was reduced by 85% at peak power.
Bore and stroke remain at 96 x 62,1 mm with a compression ratio of 13,5: 1. A gear position sensor enables the use of three specific ignition maps for gears 1 and 2, 3 as well as 4 and 5. The legendary reliability has always been a big factor in the success of the CRF450RX. When it comes to lubrication, a 5-hole jet nozzle for oil cooling of the piston and a double 12 mm drum suction pump for the oil supply are used.
In order to save even more precious weight, the magnesium cylinder head cover was redesigned with thinner walls and the fuel pump was made smaller. It is now secured with 4 instead of 6 screws, saves 120 g and offers the same pressure and the same filter life as the previous design.
Electronics of the 2021 Honda CRF450RX Enduro
- Honda Selectable Torque Control (HSTC) with 3 driving modes plus OFF
- The HRC Launch Control offers 3 start options
- The Engine Mode Select Button (EMSB) has 3 maps for setting the engine characteristics
- HSTC button now integrated in the left handlebar fitting
- Improved HRC setting tool for changes to the "aggressive" and "smooth" modes
The HSTC traction control introduced for the 2020 model year on the CRF450RX is unchanged in the 2021 version. It minimizes rear wheel spin (and therefore loss of propulsion) and maximizes traction. It does not use a wheel speed sensor and maintains the driver's feel for the throttle while controlling the power. As soon as the system detects that the speed change has exceeded a specified value, the ignition point is delayed and the injection control is checked via PGM-FI.
The three modes of the HSTC differ in the management of the drive for different driving conditions:
In Mode 1 the system intervenes least and late - this is useful to reduce wheel spin and maintain control in tight corners.
In Mode 3 the system intervenes faster and stronger and is therefore mainly used in more slippery, muddy conditions.
Mode 2 naturally offers an average value between modes 1 and 3 in terms of speed and strength of the intervention.
An eye-catching update for the 2021 model year are the driver controls and the display switchgear. The start control display, the EFI warning, the EMSB mode button and the LED display are located on the left handlebar, with the HSTC button now also being integrated here. By pressing and holding the HSTC button for 0,5 seconds, the system switches to the next mode, whereby a green LED - single flashing for mode 1, twice for mode 2 and three times for mode 3 - confirms the selection.
The HSTC system can also be switched off completely. When the engine is switched on, the system uses the last setting selected. HRC Launch Control offers every driver the best option for the best possible start. Here, too, there are three modes to choose from:
- Level 3 - 8.250 revolutions per minute, muddy conditions / beginners.
- Level 2 - 8.500 RPM, dry conditions / standard.
- Level 1 - 9.500 RPM, dry conditions / expert.
The HRC Launch Control is easy to activate: switch it on, pull the clutch and press the start button on the right. The purple LED flashes once to select level 1. After pressing the start button again for 0,5 s or longer, the LED flashes twice for level 2. After repeating the process, the LED flashes three times, indicating that level 3 has been selected.
The selection button for the motor mode (EMSB) changes the properties of the motor. There are three maps available to take into account the driving conditions or the driver's preferences:
- Mode 1 - standard
- Mode 2 - Soft
- Mode 3 - Aggressive
The LED also shows the selected mode, but with a blue light.
With an update to the 2021 mapping, the HRC setting tool can now activate a much more easily drivable smooth mode, including a smoother throttle response for beginners in this performance class. It can also program the aggressive mode into the engine management system with a very sensitive throttle valve reaction and direct engine response for demanding test and racing conditions.
Photos: Honda
Technical specifications:
| MOTOR | |
| Type | 4-stroke single cylinder, Uni-Cam, liquid-cooled |
| Capacity | 449,7 cc |
| Bore / stroke | 96,0 mm x 62,1 mm |
| compression ratio | 13,5:1 |
| FUEL SYSTEM | |
| mixture preparation | injection |
| Tankinhalt | 8 l |
| ELECTRICAL SYSTEM | |
| ignition | Digital CDI |
| Starter | electric |
| DRIVE TRAIN | |
| Clutch | Multi-disc clutch, wet |
| Translation | Claw gear |
| Final drive | Chain |
| FRAME | |
| Type | Aluminum double loop tubular frame |
| LANDING GEAR | |
| Dimensions (L´B´H) | 2.182 839 x x 1.282mm |
| wheelbase | 1.477 mm |
| Steering head angle | 27,2° |
| trailing | 115 mm |
| seat height | 965 mm |
| ground clearance | 336 mm |
| Weight ready to drive | 107,6 kg |
| SPRING ELEMENTS | |
| your Front Wheel. | Showa 49mm USD fork |
| behind | Showa monoshock with Honda Pro-Link lever system |
| BIKES | |
| your Front Wheel. | Aluminum spoked wheel |
| behind | Aluminum spoked wheel |
| Front tire | 90 / 90-21M Dunlop Geomax AT81F |
| Tire behind | 120 / 90-18M Dunlop Geomax AT81 |
| BRAKES | |
| your Front Wheel. | Single disc brake 260 mm |
| behind | Single disc brake 240 mm |
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