The new 2011 Kawasaki KX450F has a race-ready engine is compact and light, with a short 100mm cylinder head and a 12.5:1 compression ratio. A wedge-shaped crank offsets 60 percent of the crankshaft's reciprocating weight, producing an effective "counterweight" effect.
This is on par with Kawasaki's factory racers and helps reduce engine vibration, smooths power delivery and enhance low-rpm throttle response. A stainless steel exhaust pipe connects to the revised silencer, which uses long-fiber packing material to maximize service intervals.
A rubber-damping collar in the rear silencer mount provides a boost to long-term durability. The KX450F's Digital Fuel Injection (DFI) automatically adjusts to suit track and climate conditions, and offers stable fuel metering even when landing from jumps in tough motocross conditions.
The DFI system includes a compact and lightweight ECU, a 43mm throttle body, a lightweight aluminum fuel pump and an ultra-fine atomizing injector. Set at a 45-degree angle for ideal mid-range power, the 10-hole injector sprays precise, 60-micron fuel particles for smooth power delivery and accurate engine response throughout the rpm range.
Designed specifically for motocross, the KX450F's lightweight DFI system doesn't require a battery; the engine can be started within three rotations of the crankshaft using only the electricity generated through the initial stroke of the kickstarter.
An optional ECU Setting Tool allows racers to select from several different ECU data maps, or fine-tune a custom map that alters fuel injection and ignition timing to suit different tracks and conditions. The tool can also be used as a data logger, recording up to six hours of data, including engine rpm, degree of throttle opening, engine boost, coolant and air temperatures, ignition timing, fuel adjustments, gear position and system voltage.
Engine Overview
• 449cc liquid-cooled, DOHC, four-stroke single
• Bridged-box
bottom piston design offers optimal engine performance
• Reinforced
crankcase is strong and durable
• A forward
lean angle of 3 degrees puts the engine in the ideal position for
maximum traction
• Tuned for a
broad powerband with the torque curve set just under the wheelspin
threshold
•
High-acceleration cams help the engine rev quickly
•
Maintenance-free automatic cam chain adjuster
• Large
airbox flap helps prevent mud and water from entering
Bridged-box Bottom Piston
• Same design as used on our factory racers; offers improved
performance at all rpm
• Lighter and
more durable than traditional piston designs
• Short
piston skirt features low-friction coating for reduced mechanical losses
• Reinforced
external ribs for strength and durability
• Revised
profile with fully flush internal bracing results in a lighter, stronger
piston
• Short
piston pin offers increased strength
Cylinder Head
• Compact head is only 100mm tall
• 36mm
titanium intake and 31mm exhaust valves with aluminum spring retainers
minimize reciprocating weight and cylinder height to help ensure
reliable valve control at high rpm
• Double
valve springs allow a short cylinder head height and help ensure stable
valve operation
• Camshafts,
lobes and tappet surfaces feature a soft-nitride treatment for long wear
and high-rpm reliability
Crankshaft
• Crankshaft with high inertial mass helps maximize rear wheel
traction
•
Wedge-shaped crank web provides enough offsetting moment for a 60
percent balance factor – and is similar to the crank balance in
Kawasaki’s factory race engines, resulting in reduced engine vibration,
smoother power delivery and increased performance, with a noticeably
snappier response at low rpm
• Crankshaft
and connecting rod feature a special carburizing and quenching treatment
to maximize rigidity
Front Fork
• Race-oriented suspension settings offer maximum overall
performance
• Revised
damping settings offer improved action and increased comfort during the
initial phase of the suspension stroke
• Kayaba
Air-Oil-Separate (AOS) fork keeps oil and air in separate chambers for
stable damping performance during long motos. Low-friction fork seals
contribute to smooth action
•
Diamond-like Carbon (DLC) coating on the outer surface of the inner fork
tubes offers minimum stiction when the fork is exposed to lateral
forces that would usually hamper slide action. The result is improved
fork response, especially during cornering
•
Friction-reducing Kashima Coat on the inside of the fork’s outer tubes
contributes to smooth suspension action (especially at the initial part
of the stroke) and a superb ride feel
• Wrap-around
fork tube guards offer effective protection for the sliders
Rear Shock
• New damping settings contribute to increased stability and
improved impact performance when landing from jumps
• Rear
suspension settings and linkage ratios derived from extensive rider
testing
• Kayaba rear
shock features a large 50mm piston
• Rear shock
features dual compression adjustability, allowing high-speed and
low-speed damping to be tuned separately
• Also
features Kashima Coat treatment on the cylinder for reduced friction and
smoother suspension action
• Easy
adjuster access for track-side suspension tuning
easy Starting
• Strong output from the large ACG rotor provides enough
electrical power for the battery-less FI system to enable true one-kick
starting without using a battery
• Equipped
with an automatic compression release (ACR) system for quick and easy
starting. The dual-weight centrifugal decompression system is fitted to
the exhaust cam
• Compression
release features 1.0mm of valve lift, to minimize the required kicking
power
Efficient Cooling
• High-capacity Denso radiators feature tightly packed cores and
a fin design that delivers superior cooling efficiency
• Radiators
don’t need reinforcing brackets, which results in lower overall weight
• Shrouds
feature a slim design that melds with the radiators’ design
• Radiator
louvers feature four small blades set at a shallow angle for minimum
overlap and maximum air flow
Strong and Durable Clutch
• Clutch assembly provides a direct feel and superb control
• Excellent
oil drainage contributes to more direct feel
• Friction
plates with substantial friction material contribute to a more direct
feel
• Large
operating plate pusher reduces the clearance between the pusher and the
input shaft hole, improving clutch operation
Close-ratio 5-speed Transmission
• 5-speed transmission and low-rpm engine response combination
offers riders more gear options for traversing rough sections or getting
into the rhythm of a course easily so they can focus more on racing
• Thinner
inner-link chain is light and strong
•
Sprocket-style chain drive roller reduces the effect of driveline lash,
helping smooth engine braking and facilitating additional corner entry
control
Additional Features
• Skid plate made of resin material offers great protection
without excess weight
• Clutch
cable boot features a large quick adjuster, making it easy for riders to
adjust play in the clutch cable on the fly
• Increased
front axle collar diameter transmits more feedback from the contact
patch to the rider
• Ribless
rear hub and butted spokes offer light weight and excellent durability
• Rear
caliper guard helps protect the caliper from damage
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