Powersports / Motorcycles / Motocross / CRF450R / Development
Honda's 2005 CRF450R - Doing More with Less
Honda refined the 450R each year thereafter, with noticeable improvements in weight reduction and increased power for 2004. This continuous process of evolution, typical of Honda's ongoing product development, carries through to the 2005 CRF450R as well. In so doing, Honda has raised the bar once again, elevating its flagship motocrosser to a level that will keep the competition in its dust.
Honda's goals for the 2005 CRF450R centered on improving the bike's already-stellar handing, refining the overall riding feel while maintaining the four-stroke's prodigious powerband. The 450R continues to lose weight, which produces benefits in a multitude of areas, including balance, maneuverability, acceleration and braking. Its dry weight has been reduced by 3.5 pounds to 218.5 pounds, an amazing achievement accomplished by a thorough review of the bike's main assemblies-engine, frame and suspension-and their many subassemblies.
The most notable weight reduction occurs in the swingarm, which features a dual-axis, double-taper design with a large cast aluminum cross-member. The assembly drops more than a half pound (8.75 ounces) compared to the 2004 model, while maintaining both its lateral and axial stiffness to preserve the CRF's excellent handling character.
More weight savings are achieved by a newly designed rear hub made of a high-strength magnesium-silicon aluminum alloy. Compared to conventional alloys, this remarkable material allowed Honda's engineers to reduce the hub's weight by 3.5 ounces (10 percent) while simultaneously producing a hub that is stronger and more rigid.
Another 12-plus ounces of weight are eliminated in the following areas:
These changes, together with the reduced front fork offset and lighter swingarm and rear hub, subtly shift the CRF's weight distribution forward for a nearly ideal front-to-rear balance.
The fourth-generation aluminum frame featured on Honda's big CRF incorporates the company's vast database of frame technology and race-winning experience. To improve turning and produce a front end feel that is lighter and yet more stable, Honda redesigned the steering head structure for less flex during cornering. By reducing rake from 26.91 to 26.79 degrees and repositioning the axle mounting point on the fork to increase trail 2mm to 109.4mm (4.30 inches), the 450R now turns even more precisely than before, providing the rider with better cornering feel while also maintaining the bike's legendary stability.
To make the frame even more race-ready, it features larger rectangular-section downtubes and stronger gusseting throughout. In addition, taller swingarm pivot plates and thinner top frame spars create a narrower overall frame cross-section for even better rider comfort and maneuverability. Narrower, thicker radiators that better centralize the 450R's mass also allow narrower shrouds for improved ergonomics. Despite the numerous measures taken to strengthen the frame and modify its ergonomics, overall frame weight is virtually unchanged.
The CRF450R's power flows from its 449cc liquid-cooled four-valve Unicam™ single-cylinder engine. Churning out massive amounts of power and torque, the 2005 model is fitted with a new airbox and intake tube that produce a more direct airflow to the engine, delivering power across a broader rpm-range. New side numberplates with built-in air vents also increase airflow. Horsepower peaks at 55 bhp at 9000 rpm and the overall power curve is now more muscular than ever, with more run-out on the top end as well.
Other engine/drivetrain improvements include:
In the suspension department, Honda has lowered the rear shock mounting point and lengthened the rear shock by 0.24 inch to complement the new fourth-generation frame. The shock linkage is altered to provide more linear damping progression and a 5.5kg rear shock spring is fitted. Both the front and rear suspension have revised valving for improved bump absorption. These changes, together with the aforementioned steering geometry changes, produce more compliant suspension action front and rear, and ensure even more precise handling.
In typical Honda fashion, a host of smaller improvements grace the new 450R, including:
Given so many significant changes, the 2005 Honda CRF450R feels like an all-new motorcycle, one that will continue the success of the 2004 model. One could make the argument that the '04 CRF450R represented the apex of motocross engineering and technology. Perhaps the most amazing aspect concerning the 2005 CRF450R is that Honda found a way to make it so much better.