HONDA CRF450R

The 2021 ERA 2021er HONDA CRF450R

All parts of the CRF450R are new for 2021, with the exception of the wheels and the engine. The comprehensive update directly benefits from the know-how that HRC was able to gain through the development of Tim Gajser's factory machine, with which he rode to the world title in 2019. The new frame and swingarm, as well as changes to geometry and suspension, save weight and significantly improve curve behavior. The engine receives improvements to the intake tract and exhaust, a new decompression system and a single exhaust pot – together this leads to a softer response and improved driving ability in the lower and middle speed range. A larger hydraulic clutch provides more control with reduced leverage. More compact plastic parts and a smaller bench increase freedom of movement.

Content:

1. Introduction
2. Model overview
3. The main features
4. Technical specifications

1. Introduction

The Honda CRF450R has been the benchmark for motocross motorcycles since its introduction in 2002 and has become an epitome of balance and agility in the sum of its characteristics. This means that it always offers the driver – whether amateur or professional racer – total control and thus the opportunity to bring the driving skills to the best possible level on the slopes. In addition, the CRF of course has the very high quality, durability and durability for which Honda has long been famous.

In addition, the CRF450R is a machine that has been constantly evolving, based on the experience of Honda's global commitment to racing. After this 17-year success story, Europe's most popular open-class MX machine has now been redesigned from the ground up with the "ABSOLUTE HOLESHOT!" development concept – including a completely new chassis and a significant increase in performance in the upper speed range thanks to a brand new engine.

The standard electric starter was already a practical addition to the 2018 model, and by 2019, a cylinder head newly developed by HRC significantly increased peak performance and torque. Other updates included HRC's Launch Control and a revised stiffness balance for frame and swingarm, a new front brake caliper and a Renthal fat bar handlebar with adjustable mounting.

For the 2020 season, the CRF450R also received the Honda Selectable Torque Control (HSTC). This traction control already worked in the CRF450RW HRC racing machine, which was driven by Tim Gajser (#243) to the MX GP World Championship 2019. The CRF450R of the 2021 season is based in many areas on the experience gained by Gajser and HRC on their long road to overall victory in 2019.

2. Model overview

The CRF450R's 2021 model has a wide range of enhancements and upgrades, all of which can be summarized under the development theme of razor-sharp steering. First, thanks to a revised frame and auxiliary frame, the machine is 2 kg lighter. In addition, the stiffness balance of the new frame and the swingarm in combination with a tighter chassis geometry, greater ground clearance and changes to the suspension are all geared towards optimal cornering behaviour. The findings from Tim Gajser's 2019 World Champion season reduce rider exhaustion and enable enthusiasts of all performance classes to consistently achieve optimal lap times.

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 moved, the volume of the airbox increased, the throttle housing was reworked and the outlet openings were reshaped. The exhaust manifold is also new, and a single silencer replaces the previous double silencers.

In addition, there is an enlarged hydraulic clutch including reduced hand power as well as 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 smaller at the back. An attractive new graphic design, completely in red, completes this comprehensive model update.

3. The main features

3.1 Chassis

Narrower pipes on the main frame and a new rear auxiliary frame save weight, drawing on HRC's know-how

• Narrower tubes and swinging pivot point at the rear wheel swingarm, including revised balance of swinging stiffness
• Geometry changes in combination with the above changes improve the steering behavior
• Front fork with new damping valves and 5 mm more travel, combined with a rear shock absorber also working with new damping valves
• Improved ergonomics with a smaller new bench and more compact, redesigned plastic parts

The double-loop aluminium frame of the CRF450R remained unchanged in the 2020 model. For the 2021 season, it has now been completely renewed with direct input from the HRC racing team to improve every aspect of cornering behaviour.

Thanks to narrower pipes, the main frame of 8.4 kg now weighs 700 g less than its predecessor, while a newly designed auxiliary frame with now 910 g also saves 320 g. Chassis dynamics are also new: while torsional stiffness is maintained, side stiffness has been reduced by 20% to increase cornering speed, traction and steering accuracy. The aluminium swingarm has a new stiffness balance matched to the frame with narrower tubes and pivot point. The pro-link ratio has also been revised.

Both the upper and lower fork bridges have been redesigned. They now offer more flex for faster steering and better steering feel. The fully adjustable 49 mm Showa USD suspension fork is a variant of the Showa "factory" fork delivered to MX racing teams in the Japanese Championship. With the aim of improving, softer cornering behaviour, the forks were reworked: the travel increased by 5 mm to 310 mm and the stiffness of the axle clamps was increased. The main piston valve of 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, saving another 200g in weight.

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 expand and install. Maintenance has also been simplified by reducing the number of 8 mm screws that secure the bodywork 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, in addition, the tank cover has been saved.

The values for steering head angle and follow-up are now lower at 27.1° and 114 mm (previously 27.4°/116 mm) and the wheelbase is also slightly shorter at 1481 mm (1482 mm). The ground clearance increases by 8 mm to 336 mm, and the lower fork bridge now sits 6.1 mm higher at 928 mm. The radius from the swinging pivot point to the rear wheel axle holder increases by 0.9° to 14.5°, while the distance between the pivot point and the front axis holder increases by 1.8 mm to 914.6 mm. The dry weight is 105.8 kg, which is 2 kg lighter than the previous model.

Designed with Computational Flow Dynamics (CFD) technology for maximum air flow, the radiator cladding is now made of one instead of two plastic parts and has lower venting, while the radiator grilles are optimized for airflow. The 6.3-l titanium fuel tank has also been improved.

A lightweight Fatbar Flex handlebar from Renthal is standard for optimal comfort. The upper fork bridge has two handlebar brackets, which allow the handlebars to be moved 26 mm to the rear and front. If the holder is rotated by 180°, the handlebars can be moved by a further 10 mm from the base position, resulting in four individual driving positions. In terms of weight savings, many smaller amounts also lead to success ("Enough dust can form a mountain," as a Japanese proverb puts it); in this sense, the now optimized cabling of the machine saves another 100 g.

At the front, a double piston brake caliper with 30 and 27 mm piston diameter and a 260 mm wave disc is used. Together with the low-expansion brake hose, 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 aluminium rims are painted black; the front wheel rim is 21 x 1.6 inches, the rear wheel rim 19 x 2.15 inches in size. The rear wheel is both stronger and lighter on the 2021 model. Dunlop MX33F/MX33 cross tyres are mounted as standard tyres.

An eye-catching, new and completely red graphic concept underlines the now even sharper lines of the 2021 CRF450R.

3.2 Motor 

• Larger airbox plus redesigned throttle housing and outlet openings for more power in the lower speed range
• New exhaust manifold and new single silencer increase torque and save weight
• An enlarged hydraulic coupling replaces the cable pull actuation and ensures uniform operation and low hand forces
• Revised decompression system reduces the risk of death

After an increase in performance of 1.8 kW at the top, plus 2 Nm more torque and more power in the lower speed range of the 2019 model, the further development of the 449.7 cc four-valve Unicam engine for 2020 focused on optimizing the PGM-FI mapping and the HRC launch control as well as on the integration of the new traction control Honda Selectable Torque Control (HSTC). The new machine for 2021 focuses on upgrades derived directly from Tim Gajser's HRC World Champion machine: they bring significant improvements in lower to medium speed driveability and 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 speeds, which is the result of an airbox increased by 1.8 l to 4.1 l. This is now easily accessible by removing a side cladding screw and feeds a redesigned, lighter 46 mm throttle housing. It optimizes the efficiency in the intake tract and actively uses the latent evaporation heat that is generated in the intake channels.

The injection nozzle angle has been increased from 30° to 60°, whereby the fuel is sprayed in the opposite direction to the intake air in the direction of the throttle valve. This improves the suction efficiency, the cooling of the mixture and the important "throttle flap feeling" for the driver. The decompression system is also new: its counterweight is shifted from the right side of the camshaft to the left, resulting in more stable operation at low speeds with a lower risk of death.

The biggest change concerns the dual outlet channels: as with the CBR1000RR-R Fireblade, its output is oval instead of round to improve their efficiency. The 5.08 kg 2-1-2 exhaust system of the previous model has now been replaced by a single system of manifolds and silencers weighing only 3.84 kg (which also eliminates a heat shield), which saves a total of 1.24 kg. The manifold is also mounted 74 mm closer to the central axle (which improves driver ergonomics), while the silencer is equipped with double resonators that both reduce noise and increase performance.

One innovation derived directly from Gajser's World Championship motorcycle is the installation of a hydraulic clutch. This improves both the control and the feeling on the lever (it works 10% lighter) and ensures a smooth lever spacing under difficult driving conditions. The coupling capacity has been increased by 27% with an additional disc (from 7 to 8 discs) and works with an additional spring to maximize power transmission and durability. Slip has been reduced by 85% at peak performance.

The bore and stroke remain at 96 x 62.1 mm at a compression ratio of 13.5:1. A gear position sensor allows the use of three specific ignition characteristics for gear levels 1 and 2, 3 and 4 and 5. Legendary reliability has always been a major factor in the success of the CRF450R. In terms of lubrication, a 5-hole jet nozzle for oil cooling of the piston and a double 12 mm barrel suction pump for oil supply are used.

In order to save even more precious weight, the magnesium cylinder head cover with thinner wall thicknesses was redesigned and the fuel pump was reduced. It is now secured with 4 instead of 6 screws, saves 120 g and offers the same pressure and filter life as the previous design.

3.3 Electronics 

• Honda Selectable Torque Control (HSTC) with 3 driving modes plus OFF
• THE HRC-Launch Control offers 3 launch options
• The Engine Mode Select Button (EMSB) has 3 characteristics for adjusting the motor characteristics
• HSTC button now integrated into the left handlebar valve
• Improved HRC setting tool for changes to the "aggressive" and "smooth" modes

The HSTC traction control introduced for the 2020 model year on the CRF450R is unchanged in the 2021 version. It minimizes the rotation of the rear wheel (and thus the loss of propulsion) and maximizes traction. It does not use a wheel speed sensor and gives the driver's feeling for the throttle while controlling the power. As soon as the system determines that the speed change has exceeded a specified value, the ignition time is delayed and the injection control is controlled 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 at the least and at the latest – this is useful to reduce the rotation of the wheels and maintain control in tight corners.

In mode 3, the system intervenes faster and more strongly and is therefore used especially in slippery, muddy conditions.

Mode 2 naturally provides an average between modes 1 and 3 in terms of speed and strength of the intervention.

An eye-catching update for the 2021 model year is the driver controls and the display switchgear. The start control indicator, the EFI warning, the EMSB mode button and the LED indicator are located on the left handlebar, where the HSTC button is now integrated.

By pressing and holding the HSTC button for 0.5 seconds, the system switches to the next mode, with a green LED indicator – one-time flashing for mode 1, twice for mode 2 and three times for mode 3 – confirming the selection.

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

The HRC-Launch Control offers every driver the best option for the best possible start. Here are also 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: turn 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 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 Motor Mode Selection Button (EMSB) changes the characteristics of the motor. There are three characteristics available to take into account the driving conditions or the preferences of the driver:

Mode 1 - Standard

Mode 2 - Soft

Mode 3 - Aggressive

The LED also displays the selected mode, but with blue light.

With an upgrade to 2021 mapping, the HRC setting tool can now activate a much easier-to-drive smooth mode, including a smoother gas acceptance for beginners in this performance class. It can also program the aggressive mode with a very sensitive throttle response and direct motor response for racing conditions into the motor control.

4. Technical specifications

All specifications are preliminary and are not available for change.

Photos: Honda