THE 2012 KAWASAKI KX™250F: Now with Dual Injectors

 
(5/18/2011)
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For 2012, Kawasaki engineers sought to create a KX250F with even more impressive top-end performance, which they accomplished by equipping its Digital Fuel Injection (DFI®) system with a second fuel injector –a first for use on production motocross bikes– located near the airbox intake. The all-new “upstream” injector helps build a wider and more potent spread of power as rpm climbs. The two fine-mist atomizing injectors that feed the 250cc four-stroke powerplant are distinct in appearance with different body sizes, but deliver the same per-cycle capacity. Together, Kawasaki’s dual injectors pack a one-two punch, delivering a second dose of fuel on acceleration to increase the high-rpm power and overrev capabilities of the KX250F.

The addition of the second injector led to multiple modifications to the DFI system. An updated Electronic Control Unit (ECU) harnesses increased ignition power to run the DFI system. An accessory 2012 calibration kit is available and uses the same connector design as 2011, but features upgraded software and is compatible with Windows 7.

The 43mm Keihin throttle body is fitted with a new seal between the air inlet port and throttle position sensor unit designed to prevent fuel penetration from the upstream injector. The 2012 KX250F is also fitted with an air boot specifically altered to allow room for the upstream injector.

The dual-injector system is the central highlight of revisions made to the 2012 KX250F, but engineers didn’t stop there in their efforts to hone this 250cc masterpiece. A host of subtle changes throughout the motor continue to make it stronger and more durable throughout, all without weighing heavily on the price tag!

An upgraded crankshaft with redistributed inertial balance harmonizes with the more potent power delivery and also helps improve reliability. The bridged box-bottom piston and cylinder walls both feature new surface treatments to minimize wear and enhance long-term durability.
Modifications to the crankshaft, connecting rod, ACG stator and rotor change their rotational inertia, enhance durability and help provide a masterful balance to the high-performance engine. Overall, the crankshaft assembly features a balance factor of nearly 60 percent, which is right on par with factory Kawasaki race machines.
 

The seamless power delivery of the upgraded engine and DFI system is supplemented by a handful of transmission upgrades. A slightly shorter stroke of the shift fork and solid (rather than hollow) more smooth shift rods give the rider a more positive feel when changing gears, while keeping shift action as silky smooth as ever. The smooth-shifting transmission and reliably consistent clutch help keep the engine in the thick of its powerband throughout even the most challenging laps.

Sharp new styling touches enhance the appearance of the upgraded powertrain. The oil filler cap and engine plugs are colored blue, matching blue accents on the suspension adjusters and stylish new graphics.

Following the success of the 2011 KX250F and its impressive Separate Function Fork (SFF), the front suspension on the 2012 machine could have remained entirely untouched and still been a class leader. However, never content to leave exceptional alone, Kawasaki engineers analyzed feedback from the race teams and massaged the second-generation SFF accordingly.
Fork spring rate is higher for 2012, going from a 9.1N/mm to a 9.5N/mm. A new, longer rebound spring improves corner approach and offers a more supple initial feel. In the left fork tube’s damper stack, the valving has been adjusted to complement the heavier spring rate.  Two key features that retained from last year are the external fork preload adjuster and the trick titanium coating on the outer surface of the inner fork tubes.

The Showa-built shock also receives a stiffer spring rate, advancing from 51N/mm to 53N/mm. Along with a re-valve on the shock body, the compression damping restrictor and piston rod specs have been enhanced to refine the action of the shock. Complementing the shock upgrades is a thinner tie-rod on the suspension linkage with less rigidity, for smooth suspension action and improved traction. These refinements improve rear wheel traction and allow the KX250F to put the power down more effectively, making it easier than ever to grab the holeshot.
 

The KX250F is frequently praised for its rider interface and natural layout that fits a variety of sizes and abilities. Sleek and attractive bodywork includes a one-piece shroud and number-plate design. For 2012 the KX250F receives a new polyurethane seat that is more resistant to wear. The remainder of the chassis retains its finely crafted balance allowing the rider to have optimum leverage at all contact points for maximum performance gains on the track.

The KX250F is finished with quality race-proven components such as a Renthal aluminum handlebar and black alumite-coated aluminum wheels that are both lightweight and incredibly strong. A sleek, ribless rear hub and butted spokes further reduce unsprung weight, and factory-style graphics with a splash of blue that matches the alumite suspension adjusters and engine plugs finish off the sophisticated look of the class-winning machine, which is bound to top plenty of race podiums and enthusiast publication shootouts in the coming year.
Racers who ride their KX250F at designated events are eligible to receive support from Team Green™, Kawasaki’s amateur racing support program. Each year, Team Green provides regional support vehicles and highly trained technicians at more than 100 events throughout the United States, offering technical information and assistance to those who race Kawasaki products. Kawasaki also offers a comprehensive contingency program for amateur and professional riders who place well at designated events.
2011 Kawasaki KX™250F

Features and Benefits

At a Glance…
New dual injector Digital Fuel Injection system
More robust high-rpm engine output extends deep into the overrev
Revised transmission offers improved shifting action and durability
Thicker, stronger engine components improve reliability
Revised Showa Separate Function Fork (SFF) offers more supple initial hit, and improved action during corner entry
Increased spring rates on front and rear suspension enhance traction and offer a more solid feel

High-revving, High Performance Engine
249cc, liquid-cooled, four-stroke, four-valve, single-cylinder DOHC engine delivers hard-hitting power across the rpm range
Improved decompressor spring action for easier starting
New nickel plating on cylinder walls has a higher adhesion factor for increased durability
New connecting rod has a thicker stem for improved reliability
New more rigid crankshaft is re-balanced for better performance and higher durability
Thicker crank web design features a balance factor on par with the factory racers for reduced engine vibration, smoother power delivery and increased performance in the mid-high rpm range
Revised ACG stator and rotor inertia complements the changes made to the crankshaft

Digital Fuel Injection (DFI) System
Upgraded system adds a new “upstream” injector located closer to the airbox
All-new second injector features different body size, but same capacity as primary injector
Added seal between air inlet port and throttle position sensor unit on the 43mm throttle body protects TPS sensor from fuel penetration
Progressive throttle linkage opens more quickly after 3/8 open position
Simple and efficient system: No battery, fuses or relays
Sharp and precise engine response across entire rpm range
Offers easy engine starting
Helps prevent engine hesitation after landing from jumps and other high-impact situations
Optional accessory calibration Kit features new 6-pin connector type allows easy tunability
Optional accessory FI Indicator Light allows the DFI system to communicate diagnostic information

Bridged Box-Bottom Piston
Light and strong piston shares same design as the factory racers, with a new tin plating to optimize its interface with the new nickel plating on the cylinder wall
Changed shape of streak finish improves lubrication and wear resistance
Short piston pin reduces reciprocating weight
Lightweight and Efficient Top End
Lightweight, highly rigid, titanium 31mm intake and 25mm exhaust valves reduce reciprocating weight and offer high-rpm reliability
Ultra-light valves have extremely thin valve stems on par with those found in supersport machines; intake valves feature thick heads for increased strength
Intake ports designed for peak performance at all rpm, especially in the high-rpm range
Special casting method leaves the intake port surfaces extremely smooth for optimum intake efficiency across the rev range
Silicon-coated head gasket provides excellent sealing
 
Stainless Steel Exhaust System
Stainless steel construction offers extra durability
High-volume muffler assembly keeps noise levels at 94 dB while retaining power production
Joint between pipe and muffler offers excellent sealing, while a rubber damper collar on the rear silencer mount equals serious durability

Efficient Cooling System
Thick and wide radiators are strong and offer excellent resistance to mud buildup while providing superb cooling performance
Cylinder head water jacket routes coolant to the front of the cylinder head for even cooling

Transmission and Shifting
Shorter shift fork stroke and more smooth solid shift forks (not hollow) offer improved shifting action
Strong, beefy crankcases feature additional material around the engine mounts to help increase long-term durability
Clutch cable holder is integrated with the crankcase for accurate feel at the clutch lever
Scavenge oil filter screen can be accessed without splitting the crankcases, facilitating easier maintenance

Quick-turning Chassis
Utilizes a low-rigidity steering stem for lighter handling
The KX250F’s slim and lightweight aluminum perimeter frame is composed of forged, extruded and cast parts
Center of gravity and key dimensions such as swingarm pivot, output sprocket and rear axle locations designed to increase forward drive with minimal rear-end squat
Upper engine mounts on head cover sides increase overall rigidity

Race-oriented Suspension
Revised race-oriented suspension features heavier spring rates and revised damping settings both front and rear
Separate Function Fork (SFF) separates springing and damping functions for less weight, better performance, less stiction and easier adjustability
Fork features the only external spring preload adjustability in its class
Super-hard titanium coating on the outer surface of the inner fork tubes reduces stiction and improves suspension action while also helping prevent scratches and tube damage
Friction-reducing Kashima Coat treatment on the inside of the outer fork tubes contributes to smoother suspension action
Wrap-around fork tube guards provide greater protection for the inner tubes
Altered piston rod specs improve shock setting flexibility and offer better rear wheel traction
Features Kashima Coat on the inside of the shock reservoir for reduced friction and smoother suspension action
Rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately
Superior Rear-wheel Traction
Swingarm features optimum internal bracing and flex characteristics for superb cornering performance
Alloy swingarm uses a cast front section, tapered hydroformed spars and forged chain adjusters
Uni-Trak® rear suspension linkage system mounts the suspension arm below the swingarm, allowing more rear suspension stroke and precise tuning
Linkage system receives upgraded tie-rod which has less rigidity for smoother suspension action and improved traction
Linkage ratios for the Uni-Trak rear suspension match rear shock damping settings to achieve maximum rear wheel traction

Rider Interface
Bodywork components offer the rider a slim interface, making it easy for racers to feel comfortable and go fast
Formed using a double-injection molding process, the two-tone shrouds offer a slim design
Side number plates also two-toned and contribute to the slim package
Right side panel has an added passageway to help cool the silencer
Frame is wider at the ankles to offer better grip and narrows near the bend below the seat to allow a slim riding position
Slim seat features upgraded polyurethane, designed for greater durability
Seat has a slip-resistant top and side surface for good grip when seated and while standing
50mm wide (front-to-rear) footpegs offer superb grip and feel at the pegs
Clutch cable boot features a large quick adjuster, making it easy for riders to adjust play in the clutch cable while on the fly
Throttle grip has a one-piece collar that provides additional stability during throttle operation
Lightweight short-length grips feature a pattern designed to provide excellent grip

Factory-style Components
Black alumite-coated rims, just like the factory racers
Titanium coated inner fork tubes to minimize stiction
Lightweight rims offer maximum strength and weight savings
Thick and rigid front fender
Rear brake pad material offers powerful braking performance
Front and rear petal brake discs help reduce unsprung weight, and the wave shape helps clean the brake pads for more efficient stopping performance
Rear caliper guard protects caliper from damage
Ribless rear hub and butted spokes further reduce unsprung weight
Renthal aluminum handlebar is standard equipment
Blue ignition cover plugs and oil filler cap match the blue accents on the factory race bikes
Factory-style graphics complement the KX250F’s highly tuned performance

Additional Features
New countershaft sprocket cover improves look
New polyurethane resin drive chain roller reduces weight
Redesigned air boot allows room for second fuel injector
Large resin skid plate offers great protection with minimum weight

 


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WARNING: Much of the action depict­ed in this magazine is potentially dan­gerous. Virtually all of the riders seen in our photos are experienced ex­perts or professionals. Do not at­tempt to duplicate any stunts that are be­yond your own capabilities. Always wear the appropriate safety gear.

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