Kawasaki USA has unveiled a new 2021 KX250 and a revised KX450. There is no news on price, availability or spec for Europe yet, though. The 2021 KX250 builds on the engine changes from the previous year to deliver even more power and make it the most powerful KX250 to date. In addition to its high revving engine, it now features new electric start, new Belleville washer spring hydraulic clutch, and a new slim aluminium perimeter frame that improves handling to enable quicker lap times, making the KX250 even more potent on the racetrack.

The KX250 motorcycle is instilled with a high level of technology and KX DNA so that you can be the next moto prodigy. Its power, handling and adjustability personalize the feel of the motorcycle and provide higher confidence for motocross riding at all levels. The powerful engine of the KX250 features upgrades to both the top and bottom end for increased power, improved brakes offer more control when harnessing the power of the stronger engine, and an updated KX450-style frame and fine-tuned suspension settings to create the ultimate performance package.

Highlights of changes for 2021

• New more powerful engine
• New Electric start
• New Belleville washer hydraulic clutch
• New Lightweight aluminum perimeter frame
• New Fine-tuned race-ready suspension and brake components
• New Slim, ergonomic bodywork

ENGINE
• New engine with increased peak power
• New processing for intake and exhaust ports
• New exhaust cam timing
• New stiffer valve springs
• New combustion chamber design and flatter piston crown
• New longer connecting rod
• New lighter crankshaft design
• New revised pressure balance inside the crankcase
• New Belleville washer spring hydraulic clutch
• New electric start via the push of a button
• New lightweight, compact Li-ion battery

Despite the 2020 model already benefitting from a significant power increase thanks to its adoption of finger-follower valve actuation, the engine of the 2021 KX250 has received additional changes to raise peak power even further and enable an even higher rev limit, while significantly increasing low-mid range performance.

Tuned to best suit race-experienced riders, the 249cc liquid-cooled, four-stroke engine focuses on more top-end revs thanks to improvements gleaned through Kawasaki’s factory racing efforts.

The 2021 KX250 becomes Kawasaki’s first electric start 250 motocross bike, which is activated by the push of a button located on the handlebar near the right grip, making starting easy and convenient. The ability to restart the engine quickly can mean the difference between keeping your lead or having to fight your way through the pack under intense race situations. A lightweight, compact Li-ion battery helps keep weight down, as does an automatic centrifugal decompression system fitted to the exhaust cam, which lifts one exhaust valve to facilitate starting.

In addition to an electric start, the 2021 KX250 also becomes Kawasaki’s first 250 Kawasaki motocross bike equipped with a Belleville washer spring hydraulic clutch. The new high-capacity Belleville washer spring clutch offers a more direct feel and an easier pull for lighter lever action, reducing fatigue while on the racetrack. The use of Belleville washer contributes to lighter clutch actuation when the lever is pulled in, and a wider clutch engagement range, which facilitates control. In order to promote clean separation and help reduce drag when the clutch is pulled in, the friction plates were designed with offset segments. The hydraulic clutch is designed to provide a more consistent feeling through minimal change in clutch play as the clutch heats up during heavy use.

Utilizing the finger-follower valve actuation – a valve train designed by Kawasaki’s World Superbike engineers – helps achieve a high rev limit and allows for the use of more aggressive cam profiles, which contributes to high rpm performance. A diamond-like carbon coating on the finger followers helps protect against wear. Complementing the aggressive cams are large-diameter intake and exhaust valves with high lift, which flow more air and contribute to strong power. The processing for the intake and exhaust ports has been revised with a new, larger-diameter angle that contributes to increased performance.

The cams benefit from a thin and highly durable gas soft-nitride treatment to reduce wear and increase high rpm reliability and the exhaust cam timing has been retarded 3º for better engine performance. Lightweight titanium valves reduce reciprocating weight and offer high rpm reliability, while the valve springs now feature a higher spring rate to match the higher rev limit. The addition of a 3mm longer connecting rod decreases the lateral force on the cylinder walls as the piston moves up and down, helping to reduce mechanical loss and improving reliability. The cylinder is offset 3mm forward, reducing mechanical loss and increasing engine performance. A cylinder head-mounted cam chain tensioner adds to the KX250’s dependability by offsetting the increased loads from the aggressive camshaft and high revving engine.

A plateau honing process of the cylinder bore results in a smooth surface with good oil-retention. The smooth surface also helps to reduce mechanical loss and improve power. A revised combustion chamber design and a flatter piston crown contribute to increased performance. The high-performance piston features the same design used by Kawasaki’s factory racers and contributes strong performance at all rpm. A short skirt, reinforced external ribs and the use of a bridged-box piston, featuring internal bracing, allowing for a lightweight and strong piston design. A dry film lubricant coating on the piston skirts reduces friction at low rpm and helps with the piston bedding-in process.

To reduce weight, an update has been made to the crankshaft web design and the pressure balance has been revised inside the crankcase, adding to the engine’s increased performance. Low-friction plain bearings on the crankshaft pin help reduce mechanical loss and lift overall performance. For strengthening of the transmission, axle spacing has been revised to match the increased engine output. Along with matching the revised axle spacing, shape-optimized gears contribute to weight reduction.

The airbox construction features a shorter, tapered intake funnel, contributing to increased high rpm performance. The KX250 was the first production motocross bike with dual injectors an injector downstream of the throttle valve that is tasked with delivering a smooth, instant response, and a second, upstream injector located close to the airbox for a significant contribution to engine output at high rpm. The exhaust system length helps increase high rpm performance and the hydro-formed joint pipe features a reverse taper design. A large throttle body flows a great volume of air and provides a boost in high rpm performance.

Adding to Kawasaki’s engineering efforts for optimized airflow is the positioning of the intake duct for a straight approach for intake air. The downdraft-style intake routing increases the intake air’s approach angle into the cylinder, improving cylinder-filling efficiency and increasing the engines power.

DFI COUPLERS

Contributing to the race-winning engine characteristics, the digital fuel injection system of the KX250 features a coupler package that has set the industry standard. Each KX250 motorcycle comes standard with three different couplers, easily allowing riders to select pre-programmed fuel injection and ignition mapping to suit their riding style or track conditions. The four-pin DFI couplers select maps that are designed for standard, hard or soft terrain settings. Changing the engine map is as simple as connecting the coupler cap of choice.

For riders looking to fine-tune their ECU settings, the KX FI Calibration Kit (Handheld) is offered as a Kawasaki Genuine Accessory and provides access to the fully programmable ECU. Used by the factory race teams, the handheld device eliminates the need for a trackside laptop and gives riders the ability to create custom maps for precise adjustment of fuel and ignition settings. The user-friendly device can store up to seven preset maps and is PC-compatible.

LAUNCH CONTROL

The launch control system of the KX250 motorcycle is a major advantage and favorite for riders who are focused on getting to the first turn ahead of their competition. The push-button activation retards ignition timing in first and second gear, helping maximize traction on slippery surfaces like concrete starting pads and put the bike’s potent power to the ground. Once the rider shifts into third gear, normal ignition mapping immediately resumes and full power is restored.

CHASSIS

New KX450-based slim aluminum perimeter frame
New engine is used as a stressed member
New steering head area with optimized rigidity
New KX450 swingarm for increased rear traction

The KX250’s new slim aluminum perimeter frame is based off of its KX450 counterpart and with lightweight, nimble handling, and slim ergonomics in mind. Its design is a lightweight construction composed of forged, extruded, and cast parts. The new frame offers a better overall rigidity balance, and while many of the parts are common with the KX450’s frame, the cast parts like shock tower mount and engine hangers were designed specifically for the needs of the KX250. Adding to the frame’s rigidity balance is the use of the engine as a stressed member. The steering head area, main frame rails with updated cross-sections, line for the swingarm brackets, and wider lower frame rails have all been revised and contribute to the overall rigidity balance.

The addition of a KX450 swingarm delivers the rigidity necessary to match the frame and helps to increase traction at the rear wheel. The center of gravity and key dimensions such as swingarm pivot, output sprocket and rear axle locations have all been carefully selected so that the rear tire drives the bike forward.

SUSPENSION & BRAKES

New lower triple clamp design
New revised linkage ratios
New fine-tuned front and rear suspension settings
New smaller-diameter 240mm rear disc
New KX450 front master cylinder

The KX250 is equipped with large diameter 48mm KYB inverted coil-spring front forks that offer optimum action at the initial part of the fork stroke. The forks feature large-diameter inner tubes, enabling the use of 25mm damping pistons and delivering smooth action and firm damping. The Kashima coating on the forks’ outer tubes creates a hard, low-friction surface to help prevent wear abrasion on the inside of the tubes, ensuring the sliding surfaces remain smooth over time while protecting the outside against corrosion. The lubricating material in the coat contributes to smoother suspension action and a better overall ride feel. The lower triple clamp has been revised for optimized rigidity and reduced weight while contributing to the front’s ability to absorb bumps.

In the rear, a KYB shock unit complements the front fork. The rear shock features dual compression adjustability, which allows high-speed and low-speed damping to be tuned separately. Kashima Coat on the tank cylinder helps prevent wear abrasion and reduces friction for smoother suspension action. A new Uni-Trak rear suspension system mounts the linkage arm below the swingarm, allowing a longer rear suspension stroke. The linkage ratios have been revised, now using the same as those found on the KX450 motorcycle, contributing to both increased absorption and damping performance. Both front and rear suspension feature new fine-tuned settings that are designed to match the frame and provide increased bump absorption as well as increased traction.

Contributing to the numerous factory-style racing components on the KX250 motorcycle are petal disc brakes. Upfront is an oversized 270mm Braking brand rotor, which delivers strong braking force and superb control. A new front master cylinder like the one on the KX450 adds to the high level of control and overall feedback found in the front brake.

On the rear, a new smaller-diameter 240mm Braking brand disc contributes to controllability and offers optimized stopping performance. The petal-style discs contribute to both sporty looks and help deflect debris. A rear caliper guard helps protect the caliper from damage.

ERGONOMICS & ERGO-FIT ADJUSTABLE COMPONENTS

New factory-style 1-1/8” Renthal Fatbar Handlebar

Kawasaki continues its unmatched commitment towards providing riders with class-leading comfort thanks to its Ergo-Fit adjustable handlebar mounting system and footpegs to fit a variety of riders and riding styles. New for 2021 is a factory-style 1-1/8” thick aluminum Renthal Fatbar handlebar, a popular aftermarket part that is now a standard feature. The handlebars feature four-way adjustable mounts. The multi-position handlebars offer two mounting holes with 35mm of adjustability, and the 180-degree offset clamps boast four individual settings to suit different size riders.

The footpegs feature dual-position mounting points, with a lower position that reduces the standard setting by an additional 5mm. The lower position effectively lowers the center of gravity when standing, and reduces knee angle when taller riders are seated.

BODYWORK & SEAT

New bodywork facilitates rider movement
New flatter design at the top of the fuel tank
New slimmer radiator shrouds
New smoother engine covers
New gold finish on the oil cap and generator cover plugs

Complementing the improved peak power and precise handling of the KX250 is sleek new bodywork with factory-style graphics that helps ensure it’s the sharpest looking bike in the paddock and further reflect its highly-tuned performance.

For 2021, the bodywork has been designed to facilitate rider movement with long, smooth surfaces that make it easy to slide back and forth. The seams between the shrouds, seat, and side covers are as flush as possible to help the rider move around on the bike. A revised design on the top of the fuel tank allows an even flatter progression from the seat to the tank, which gives the rider greater freedom of movement when changing riding position and facilitates sitting farther forward. The single-piece radiator shrouds are now slimmer where they come in contact with the rider’s legs and positioned closer to the frame. In-mold graphics result in an ultra-smooth surface and contribute to the KX250’s factor-racer looks.

Engine covers have been redesigned and are smooth in order to not impede rider movement. Helping the KX250 retain its factory-style look is a new gold finish on the oil cap and the two plugs on the generator cover, while the rims are coated in black alumite.

2021 KAWASAKI KX450

The Kawasaki KX450 motorcycle returns as the flagship model in the Kawasaki KX lineup for 2021 and boasts several new updates to maintain its edge as the leader in its class. Tuned to best suit race-experienced riders, the 449cc liquid-cooled, four-stroke engine with improved engine power, slim aluminum perimeter frame, Showa A-Kit technology suspension, redesigned hydraulic clutch and electric start are the ultimate combination of a championship-winning package.

The KX450 is built with race-winning components to help Kawasaki riders get to the top step of the podium. For 2021 the KX450 receives engine updates for increased performance, a new coned disk-spring hydraulic clutch, and a new 1-1/8” Renthal Fatbar handlebar. From the showroom to the racetrack, the performance of Kawasaki’s KX family of motorcycles is proof of its engineering pedigree. It truly is The Bike That Builds Champions.

ENGINE

New dry film lubricant coating on the piston skirt
New larger diameter clutch plates and revised friction material
New Belleville washer spring hydraulic clutch for improved clutch performance

The four-stroke, single-cylinder, DOHC, water-cooled 449cc lightweight engine package utilizes input derived directly from the Monster Energy Kawasaki race team, producing peak power and a torque curve that makes it easy to get on the gas early. The potent KX450 engine features an electric start, which is activated by the push of a button and powered by a compact Li-ion battery.

Kawasaki utilizes top-level road racing technology in the KX450 valve train, using designs from Kawasaki World Superbike engineers. It uses finger-follower valve actuation, enabling larger-diameter valves and more aggressive cam profiles. The intake and exhaust valves are formed from lightweight titanium, while a bridged-box piston uses the same design as the race team’s factory motorcycles. A new dry film lubricant coating on the piston skirt reduces friction between the piston and cylinder wall, contributing to increased performance.

A close-ratio five speed transmission features lightweight gears and shafts to keep weight down, yet retain strength, while contributing to the motorcycle’s winning performance. The transmission is paired with a new high-capacity Belleville washer spring hydraulic clutch for 2021. The clutch’s coil springs have been replaced with a coned disk-spring, resulting in lighter clutch actuation when the lever is pulled in, and a wider clutch engagement range to help facilitate control. Larger diameter clutch plates and revised friction material is designed to provide a consistent feeling through minimal change in play as the clutch heats up during heavy use. The friction plates feature offset segments to help promote clean separation of the discs and reduce drag when the clutch is pulled in.

CHASSIS

An industry-leading slim aluminum perimeter frame provides precise cornering through excellent front-end feel and agility when riding at high speeds. The frame’s lightweight construction is composed of forged, extruded and cast parts, while the engine is used as a stressed member and adds to the frames rigidity balance. A lightweight alloy swingarm is constructed of a cast front section and twin tapered hydro-formed spars in a raw aluminum finish, complementing the frame. Engineers carefully placed the dimension of the swingarm pivot, output sprocket and rear axle locations, helping to focus on center of gravity and balanced handling.

SUSPENSION & BRAKES

High-performance Showa 49mm coil spring front forks with A-KIT technology can be found up front, featuring large diameter inner tubes that are the same size as those found on the machines of Kawasaki’s factory racing team (KRT). The forks enable the use of large damping pistons for smooth action and firm damping.

In the rear, a new Uni-Trak linkage system is designed to work in conjunction with the Showa shock, aluminum frame and swingarm. The linkage, which is mounted below the swingarm, allows for a longer rear suspension stroke and more precise rear suspension tuning. The Showa Compact Design rear shock boasts A-Kit technology with large diameter compression adjusters, improving on the high frequency movements found on today’s motocross tracks.

An oversized 270mm, petal-shaped front brake rotor from the renowned manufacturer, Braking, is fitted to perfectly complement the powerful engine of the KX450. The rear is equipped with a 250mm petal-shaped Braking rotor that matches the large front disc.

ERGONOMICS & ERGO-FIT ADJUSTABILITY

New factory-style 1-1/8” Renthal Fatbar handlebar

New for the 2021 KX450 is a factory-style aluminum Renthal Fatbar handlebar that helps to reduce vibration and shocks transmitted to the rider through the thicker 1-1/8” handlebar. The new handlebar grip position is lower and closer to the rider, making it easier for the rider to weight the front wheel.

Kawasaki continues its unmatched commitment towards providing riders with class-leading Ergo-Fit comfort thanks to its adjustable handlebar mounting system and footpegs to fit a variety of riders and riding styles. The handlebars feature four-way adjustable mounts. The multi-position handlebars offer two mounting holes with 35mm of adjustability, and the 180-degree offset clamps boast four individual settings to suit different size riders.

BODYWORK & SEAT

Complementing the championship proven technology, the 2021 KX450 features aggressive styling along with in-mold graphics on the radiator shrouds that result in an ultra-smooth surface and racy look needed to finish at the top of its class. The sleek bodywork has been molded to match the V-mounted radiators and narrow chassis design. Each piece of the bodywork has been designed to help facilitate riders movement with long, smooth surfaces that make it easy to slide back and forth.

Kawasaki is proud to announce all-new race-ready off-road KX XC models with the all-new 2021 KX250XC and KX450XC models. These are for the USA market while there is no news yet of European or UK versions.

As a brand that has a rich history in off-road racing with more than 25 championships in WORCS, National Hare & Hound, GNCC, and Endurocross over the past 20 years, there’s no denying the all-new KX XC models are powered by technology that hails from a legacy of champions.