2021 KAWASAKI KX 250 MOTORCYCLE
The Kawasaki KX™250 motorcycle has more AMA motocross and supercross championships combined than any other manufacturer in its class and returns for 2021 with a list of enhancements that are designed to continue its winning history by keeping it the best performing bike on track. The 2021 model 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 coned disk-spring hydraulic clutch, and a new slim aluminum perimeter frame that improves handling to enable quicker lap times, making the KX250 even more potent on the racetrack. With a championship heritage that boasts 18 AMA professional titles and 189 race wins since 2004, the KX250 is the ideal platform for mid-level to expert riders looking to reach the top step of the podium.
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 KX™450-style frame and fine-tuned suspension settings to create the ultimate performance package.
Highlights of the 2021 KX250
• NEW More powerful engine
• NEW Electric start
• NEW Coned disk-spring hydraulic clutch
• NEW Lightweight aluminum perimeter frame
• NEW Fine-tuned race-ready suspension and brake components
• NEW Slim, ergonomic bodywork
• 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 Coned disk-spring hydraulic clutch
• NEW Electric start via the push of a button
• NEW Lightweight, compact Li-ion battery
Despite the 2020 KX250 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 electric start, the 2021 KX250 also becomes Kawasaki’s first 250 motocross bike equipped with a coned disk-spring hydraulic clutch. The new high-capacity coned disk-spring clutch offers a more direct feel and an easier pull for lighter lever action, reducing fatigue while on the racetrack. The use of coned disk-spring 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 3 mm longer connecting rod decreases 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 3 mm 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, allow 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.
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.
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.
• NEW KX™450-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 aluminium 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 240 mm rear disc
• NEW KX450 front master cylinder
The KX250 is equipped with large diameter 48 mm 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 25 mm damping pistons and delivering smooth action and firm damping. A Kashima Coat 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. Up front is an oversized 270 mm 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 240 mm 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 35 mm 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 5 mm. 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.
Kawasaki Team Green™ Racer Rewards
Kawasaki Team Green Racer Rewards return for the 2021 racing season with more than seven million dollars in contingency available for eligible KX riders. Team Green’s Racer Rewards program will be available at more than 240 events across the nation. Motocross racers will have more than $5.4 million up for grabs, while off-road riders will also be rewarded with more than $2.2 million available.
Color: Lime Green
To download high-resolution images, log on or register for the Kawasaki media site at http://kawasakimedia.com
Kawasaki Heavy Industries, Ltd. (KHI) started full-scale production of motorcycles over a half century ago. The first Kawasaki motorcycle engine was designed based on technical know-how garnered from the development and production of aircraft engines, and Kawasaki’s entry into the motorcycle industry was driven by the company’s constant effort to develop new technologies. Numerous new Kawasaki models introduced over the years have helped shape the market, and in the process have created enduring legends based on their unique engineering, power, design and riding pleasure. In the future, Kawasaki''s commitment to maintaining and furthering these strengths will surely give birth to new legends.
Kawasaki Motors Corp., U.S.A. (KMC) markets and distributes Kawasaki motorcycles, ATVs, side x sides, and Jet Ski® watercraft through a network of approximately 1,100 independent retailers, with close to an additional 7,700 retailers specializing in general purpose engines. KMC and its affiliates employ nearly 3,100 people in the United States, with approximately 260 of them located at KMC''s Foothill Ranch, California headquarters.
Kawasaki’s tagline, “Let the good times roll.®”, is recognized worldwide. The Kawasaki brand is synonymous with powerful, stylish and category-leading vehicles. Information about Kawasaki’s complete line of powersports products and Kawasaki affiliates can be found on the Internet at www.kawasaki.com.
Previous Motocross Articles