A true expert in versatility, the CRF450RX is just as comfortable in the tight woods of a GNCC course as it is on a high-speed WORCS or GNCC track. A close relative of the motocross-focused CRF450R, the RX maintains an aggressive, agile character, but is purpose-built for closed-course off-road competition, offering features like a dedicated ECU and suspension settings, an 18-inch rear wheel, an aluminum side stand, a large 2.1-gallon fuel tank and hand guards. As the motorcycle of choice for a variety of off-road racers, including the SLR Honda and JCR Honda teams, its race-winning performance and legendary reliability are continuously proven in the toughest conditions that off-road racing has to offer.
ENGINE / DRIVETRAIN
The CRF450RX engine boasts exceptional bottom-end and midrange power and torque, making for a linear delivery that is strong but manageable, even as the rider tires, while peak power is also very good. A five-hole piston oil jet and dual 12mm drum scavenge pump manage lubrication.
Cylinder Head: The design of the Unicam® cylinder head, with the decompressor system’s counterweight on the left end of the camshaft, contributes to combustion stability in the extremely low rpm range and for strong-but-manageable power delivery on corner exits, for example, as well as resistance to stalling. Engineers followed the direction of Team Honda HRC by optimizing the cam profile for low-end torque. As before, the cylinder head cover is magnesium, with a thin-wall design for weight savings.
Intake: The CRF450RX features a downdraft intake design that delivers strong, efficient power, and a large air boot (4.1 liters on the clean side of the air filter) achieves strong torque at low rpm. Following feedback from HRC, the 44mm throttle body ensures smooth power delivery at low speed. In addition, the narrow intake port shape and long air funnel result in strong low-end torque and crisp throttle response. The airbox is accessed with the removal of a single side panel bolt. The 60º fuel-injector angle enables the spray to reach all the way to the back of the butterfly, thus cooling the upstream side of the intake path for maximum intake efficiency and torque feel.
Exhaust: The engine’s exhaust port is centrally located, has an oval shape and is very straight, optimizing exhaust efficiency and torque characteristics. With the engine’s central exhaust-port location, the exhaust header and muffler are positioned close to the vehicle’s centerline for a slim profile, contributing to freedom of movement for the rider. The muffler is constructed with strong A6061-T6 aluminum for impact resistance and weight savings. A dual resonator design optimizes power, while simultaneously minimizing noise.
Clutch: The clutch is hydraulically actuated and has eight plates and a large volume for good durability with minimal slippage and light lever pull.
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 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:
- 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 CRF450RX’s 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
The motorcycle’s heavier components are positioned centrally and as low as possible for precise cornering without sacrificing high-speed tracking, and to achieve minimal squat under acceleration and negligible pitching during hard braking.
Frame / Swingarm / Subframe: The frame uses narrow main spars and features optimized reinforcement ribbing on the backside of the pivot plate, contributing to the low frame weight of just 18.5 pounds. Frame rigidity is optimized, allowing the front and rear suspension components to move freely and avoid binding, improving stability and bump absorption.
The subframe features a simple design that weighs just 2.0 pounds. The swingarm is narrow, providing good clearance in ruts, with rigidity tuned to maximize rear traction and cornering.
Suspension: The Pro-Link® rear-suspension system uses a Showa shock absorber with adjusters on the right side and an ultra-light steel shock spring. Because of the optimized frame rigidity, the shock moves freely, minimizing harshness, while offering hold-up for big impacts and performance in ruts.
Front suspension comprises a 49mm inverted Showa® coil-spring fork and a gas-liquid separation structure. The fork setting is paired with that of the shock, for proper front-rear balance. The upper and lower triple clamps are designed to offer a good rigidity balance for optimum handling and feel through corners.
Wheels: 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 CRF450RX comes with Dunlop’s rugged AT81 tires, designed for all around performance across a variety of off-road terrain.
The CRF450RX has slim bodywork, with a smooth junction of the radiator shroud and side panel, facilitating rider movement and cornering. Each radiator shroud is produced in a single piece instead of two separate parts, and Computational Fluid Dynamics (CFD) were used to design air-outlet vents in the shrouds. The radiator grills optimize the number of fins and their angle, maximizing cooling performance.
The seat base has rearward-facing tongues and front-located mounting tabs, easing installation, and using acceleration forces to keep the seat securely in place. The larger polyethylene fuel tank holds 2.1 gallons
Only 10 fasteners are used to secure all of the main bodywork components—both radiator shrouds, both side panels and the seat, and all of the bolts for the main bodywork parts have 8mm heads, simplifying maintenance.
A single switch cluster 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. 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 26mm.
Off-Road Features: The CRF450RX comes with a number of off-road-focused features that set it apart from its motocross-focused CRF450R sibling.
Softer suspension settings enhance performance over rocks and roots while the dedicated ECU map optimizes power delivery for low-traction off-road conditions. The 18-inch rear wheel allows for a taller tire sidewall, improving compliance over rough terrain and the 50-tooth rear sprocket (compared to the R’s 49) adapts the gearing for increased torque. A 2.1 gallon resin tank increases range between fuel stops.
Lightweight plastic handguards provide knuckle coverage from brush and roost and can be easily removed. The CRF450RX is also equipped with a forged-aluminum side stand for convenient on-trail parking.