All-New 2021 Honda CRF450R Overview

Scritto martedì 14 Luglio 2020 alle 19:39.

Nearly two decades after its introduction to the motocross world, Honda’s CRF450R begins a new chapter for 2021, this latest version inspired by a “Razor Sharp Cornering” design philosophy. Already the industry’s top-selling motocross model along with its exclusive CRF450RWE sibling, the CRF450R is guided by three main goals for 2021: improved power (particularly on corner exits), improved handling and better consistency for both bike and rider over the course of a tough moto.
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HONDA CRF 450 2021 – NUOVA!!!

2021 Honda CRF450R

A glance at the premier-class start line of an AMA Supercross main event—where red is almost invariably the predominant color this year—is all it takes to get a sense of the CRF450R’s popularity among top riders; since its 2002 introduction, it has become the benchmark motocrosser, and together with its limited-edition CRF450RWE sibling, it’s the top-selling 450cc MX model in the U.S. Nonetheless, Honda didn’t rest on its laurels for the 2021 model year, endowing the legendary machine with important updates aimed at improving power, handling and consistency.

As usual, this model draws lessons from Honda Racing Corporation’s global race program. A production version of the factory machine campaigned by two-time World Champion Tim Gajser to half of the 2020 MXGP moto wins thus far, and the basis for the motorcycle that Team Honda HRC riders Ken Roczen and Chase Sexton will field in AMA racing next season, the 2021 CRF450R represents a significant step up from what was already an extremely capable race machine.

 

2021 Honda CRF450R
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OBJECTIVES

When engineers approached the 2021 CRF450R project, they identified “Razor Sharp Cornering” as the development theme, which led to three main goals: Improve power, improve handling and improve consistency. The first point was addressed by making changes intended to increase the engine’s horsepower and torque, particularly in the bottom end of the range. The second objective was addressed by optimizing chassis rigidity, altering geometry and reducing vehicle weight. The final goal—regular, steady performance by both the machine and the rider—was pursued via updates to the clutch, as well as the vehicle layout for improved rider movement.

As is often the case, benefits overlapped, with improvements in one area leading to benefits in other areas. For example, the power and torque increase result in changes to power delivery that make the machine more manageable in corners. Similarly, the reduced weight not only aids cornering, but promotes a more consistent performance by the rider over the course of a race.

Speaking of weight savings, the reduction here is an example of something that was only achievable during an overall redesign, and only by accumulating small benefits in myriad areas. As the Japanese saying goes, “With enough dust, a mountain can form,” and in this case the mountain was represented by a 3 pound overall weight reduction compared to last year’s model.

ENGINE / DRIVETRAIN

The CRF450R engine has undergone a number of significant updates aimed at improving bottom-end and midrange power, making for a linear delivery that is strong but manageable, even as the rider tires. In addition, peak power is up .8 horsepower, above 5,000 rpm.

Head

2020 Decomp weight

2020 Decomp weight

2021 Decomp weight

2021 Decomp weight

The design of the Unicam® cylinder head has been updated, with the decompressor system’s counterweight relocated from the right end of the camshaft to the left. This improves combustion stability in the extremely low rpm range and contributes to a strong-but-manageable power delivery in corner exits, for example, as well as resistance to stalling. The magnesium cylinder head cover has also been designed with a thinner material, for weight savings.

2020 Head

2020 Head

2021 Head

2021 Head

2020 Exhaust port

2020 Exhaust port

2021 Exhaust port

2021 Exhaust port

The engine’s exhaust port has been centralized, ovalized and straightened, achieving improved exhaust efficiency and revised torque characteristics, for a linear delivery that continues into the high rpm range.

As before, a five-hole piston oil jet and dual 12 mm drum scavenge pump manage lubrication.

Intake

The CRF450R features a downdraft intake design that delivers strong, efficient power, but the air boot has been drastically enlarged (from 1.8 liters on the clean side of the air filter to 4.1 liters), resulting in better torque at low rpm. In addition, the rubber ring has been eliminated to simplify filter cleaning, with an external frame added to ensure a good seal is maintained. The air box is now accessed with the removal of a single side-panel bolt.

2020 Air box configuration.

2020 Air box configuration.

2021 Air box configuration.

2021 Air box configuration.

2020 fuel injection

2020 fuel injection

2021 fuel injection

2021 fuel injection

The angle of the fuel injector has been increased from 30º to 60º, enabling the spray to reach all the way to the back of the butterfly, thus cooling the upstream side of the intake path, improving intake efficiency and torque feel. 

2020 fuel pump

2020 fuel pump

2021 fuel pump

2021 fuel pump

In addition, the fuel pump is now smaller and 120 grams lighter. It’s affixed via a simplified mounting system using only four fasteners instead of six. Fuel pressure and filter life are both unaffected.

Exhaust

For 2021, the CRF450R makes the switch from two mufflers to one, reducing weight and improving bottom-end torque delivery. The entire exhaust system now weighs 8.5 pounds, a reduction of 2.7 pounds from the previous model.

New exhaust layout.

New exhaust layout.

2020 exhaust system

2020 exhaust system

2021 exhaust system

2021 exhaust system

With the engine’s new centralized exhaust-port location, the exhaust header is now routed 74 mm closer to the engine on the right side, while the single, right-side muffler has been reshaped to move its outer surface 13 mm inboard. The combined result is a slimmer overall vehicle body (including external parts), contributing to freedom of movement for the rider.

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Two resonators (one after the front U-bend and another at the upstream end of the muffler) boost power and reduce noise, and the heat shield has been eliminated to reduce weight.

Clutch

With an eye toward increasing clutch durability, engineers increased clutch volume by 27% while also adding an eighth clutch plate and using stiffer springs. In addition, a friction spring was added to suppress resonance and greatly improve power delivery. These changes reduce clutch slip by 85% at peak power, as measured by a chassis dynamometer.

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Hydraulic clutch

Hydraulic clutch

To facilitate clutch actuation and encourage consistent performance, a hydraulic clutch is now utilized as on the HRC factory machines. As a result, the force needed to pull the handlebar lever is reduced. Depending on where in the lever stroke the measurement is taken, the reduction can be as much as 10% compared to the previous model, even with the stiffer springs.

Electronics

A gear-position sensor allows the use of three specific ignition maps for first and second, third and fourth, and fifth gears. There are options for Standard, Smooth and Aggressive ignition maps, selectable via an all-new handlebar-mounted switch, enabling simple tuning depending on rider preference or course conditions. 

In addition, Honda Selectable Torque Control still offers three levels of intervention. HSTC monitors rpm spikes and responds by temporarily reducing torque by retarding ignition timing and controlling PGM-FI to aid rear traction. The three different modes differ in drive-management level, for differing riding conditions or rider preferences:

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  • Mode 1: The system intervenes most lightly and waits the longest to do so—useful for reducing wheel-spin and maintaining control in tight corners.
  • Mode 2: A midpoint between modes 1 and 3 in terms of how quickly and assertively the system intervenes.
  • Mode 3: The system intervenes most quickly and assertively, which helps in conditions that are slippery or muddy.

The CRF450R’s updated handlebar-mounted switch allows selection between three modes, depending on conditions and rider preference. The HSTC system can also be switched off completely. HRC Launch Control provides the best option for a strong start and also has three modes to choose from:

  • Level 1: 9,500 rpm, for high-traction conditions and/or advanced riders
  • Level 2: 8,500 rpm, for high-traction conditions and/or average riders
  • Level 3: 8,250 rpm, for slippery conditions and/or novice riders

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

CHASSIS / SUSPENSION

A number of significant chassis revisions were incorporated in order to improve cornering. With these changes, geometry is now different: Wheelbase is now 1 mm shorter (at 58.3 inches), rake is relaxed .5º (at 27.7º), trail is reduced by 2 mm (now 114 mm), the swingarm angle is .9º steeper (at 14.5º), the seat height is 5 mm taller (at 38.0 inches), ground clearance is increased by 8 mm (now 13.2 inches), and the distance from the front axle to the swingarm pivot is 1.8 mm longer (at 36.0 inches). As before, the vehicle’s heavier components are positioned centrally and as low as possible.

2021 geometry

2021 geometry

The result is improved cornering without sacrificing high-speed tracking, in addition to reduced squat under acceleration and less pitching during hard braking.

Frame / Swingarm / Subframe

An all-new frame uses narrower main spars, a redesigned downtube and features rearranged reinforcement ribbing on the backside of the pivot plate, changes that contribute to an overall weight reduction of 1.54 pounds, with the new frame weighing just 18.5 pounds. Lateral rigidity is reduced by 20%—resulting in supple feel that improves cornering—while vertical rigidity is maintained.

The new 2021 frame spars are smaller (red) than 2020 frame spars (green).

The new 2021 frame spars are smaller (red) than 2020 frame spars (green).

2020 subframe

2020 subframe

2021 subframe

2021 subframe

The subframe features a simplified design that enabled the elimination of a separate seat support, achieving an overall weight of just 2.0 pounds—over .7 pounds down from before.

2020 swingarm

2020 swingarm

2021 swingarm

2021 swingarm

In addition, the swingarm is now narrower, providing increased clearance in ruts, with rebalanced rigidity tuned to match the frame and improve rear traction and cornering.

Suspension

As before, front suspension comprises a 49 mm inverted Showa® coil-spring fork that follows the basic structure of that on the 2020 CRF450R, and a gas-liquid separation structure, but suspension stroke has been increased by 5 mm to better absorb rough terrain while also reducing pitching. In addition, the axle holders have an updated design for increased rigidity. The upper and lower triple clamps have both been redesigned as well, with rigidity rebalanced via updated reinforcement ribs, delivering increased flex characteristics for improved handling and feel through a corner.

2020 shock

2020 shock

2021 shock with super light weight spring

2021 shock with super light weight spring

The Pro-Link® rear-suspension system uses a Showa shock absorber whose shape has been adapted to work with the new frame, with adjusters moved from the left side to the right. Weight was cut here as well, by switching to an ultra-light steel shock spring.

The link ratio and rear travel has also been changed so that acceleration-triggered rear-end squat is reduced.

Wheels

As before, black D.I.D. rims deliver durable performance and good looks. Petal-style brake rotors disperse heat, and a low-expansion front brake hose gives strong feel and consistent stopping power.

The 2021 CRF450R comes with Dunlop’s excellent Geomax MX33 tires, generally considered to be the industry standard for soft to intermediate terrain. Developed with the help of top motocross pros, MX33s feature technologies that deliver superior grip, slide control, bump absorption and durability.

DESIGN

The technical changes to the CRF450R enabled the adaptation of slimmer bodywork, which facilitates rider movement. For example, the lack of a left-side muffler made possible a side panel that is 50 mm more inboard, and even the right side panel is moved 20 mm inboard thanks to the new muffler shape. Together, the changes result in a 70 mm reduction in width at the rear of the bike, substantially benefitting rider movement—and, consequentially, cornering. The junction of the radiator shroud and the side panel is smoother as well, further aiding rider movement.

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The radiator shrouds are new as well, and each is now produced in a single piece instead of two separate parts. Computational Fluid Dynamics (CFD) were used to design new air-outlet vents in the shrouds. The radiator grills have also been revised to optimize the number of fins and their angle, resulting in a 5% improvement in cooling performance, without changing vehicle width at the shrouds.

2020 seat

2020 seat

2021 seat

2021 seat

Whereas the seat was previously installed by sliding it forward onto the subframe and then securing it at the rear, the new seat base has rearward-facing tongues and front-located mounting tabs. This eases installation, and acceleration forces keep the seat securely in place. The 1.7 gallon fuel tank is once again made of lightweight titanium but has a new design, and the plastic tank cover has been eliminated.

2020 bodywork (12 bolts)

2020 bodywork (12 bolts)

2021 bodywork (8 bolts)

2021 bodywork (8 bolts)

During the model’s redesign, engineers looked for and capitalized upon every opportunity to cut weight for improved handling. For example, only 8 fasteners are used to secure all of the main bodywork components—both radiator shrouds, both side panels and the seat—instead of 12 as before. In addition, all of the bolts for the main bodywork parts now have 8 mm heads, simplifying maintenance.

New routing of cables.

New routing of cables.

A further 98 grams were cut by combining what used to be two left-side handlebar switch assemblies into a single cluster that addresses several functions: engine stop, ride-modes and Honda Selectable Torque Control (HSTC). The starter and HRC launch control are on the right side of the Renthal® Fatbar® handlebar. As before, there are two locations for the handlebar clamp, and the clamp can be turned 180º; as a result, four different mounting positions are possible, through a range of 26 mm. Routing the throttle and clutch control cables behind the handlebar instead of in front allowed for a weight reduction of 100 grams high on the bike.

Together, these changes aim to create a new benchmark in the motocross category.

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SPECIFICATIONS

  • Engine Type: 449.7cc liquid-cooled 10º single-cylinder four-stroke
  • Valve Train: Unicam® OHC, four-valve; 38mm intake, titanium; 31mm exhaust, steel
  • Bore x Stroke: 96.0mm x 62.1mm
  • Compression Ratio: 13.5:1
  • Induction: Programmed fuel-injection system (PGM-FI); 46mm throttle bore
  • Ignition: Full transistorized 
  • Starter: Push-button electric starter
  • Transmission: Constant-mesh 5-speed; manual
  • Clutch: Multiplate wet, hydraulically actuated (6 springs, 8 plates)
  • Final Drive: #520 chain; 13T/49T 
  • Fork: 49mm fully adjustable leading-axle inverted telescopic Showa coil-spring fork w/ 12.2 in. travel
  • Shock: Pro-Link system; fully adjustable Showa single shock w/ 12.4 in. wheel travel 
  • Front brake: 2-piston caliper (30mm, 27mm) hydraulic; single 260mm disc
  • Rear brake: 1-piston caliper hydraulic; single 240mm disc 
  • Front tire: Dunlop Geomax MX33 80/100-21 w/ tube
  • Rear tire: Dunlop Geomax MX33 120/80-19 w/ tube
  • Rake (Caster Angle): 27°7’ 
  • Trail: 114mm
  • Length: 85.9 in.
  • Width: 32.6 in.
  • Height: 49.9 in.
  • Ground Clearance: 13.2 in.
  • Seat Height: 38.0 in
  • Wheelbase: 58.3 in.
  • Fuel Capacity: 1.7gal
  • Color: Red
  • Curb Weight: 244 lbs.

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