New, close-ratio five-speed transmission provides more performance in a wider range of riding environments.
All-new aluminum frame is an extensively tested combination of castings, extrusions, forgings and aluminum tubing — all carefully put together to produce a chassis that takes legendary YZ handling to the next level.
Speed-Sensitive System 48mm Kayaba fork move the TCV (transfer control valves) above the fork springs, so that damping force is now controlled by piston speed; that prevents mid-stroke damping force changes, for a smoother, more precise ride.
Titanium-sprung four-way adjustable rear shock rod diameter is 2mm bigger. New, Kashima coating reduces friction for fantastic compliance and great handling.
Carburetion and exhaust changes let the 449cc four-stroke breathe free for even greater power production.
Changing the cylinder head angle and moving the dry sump oil tank inside the front of the crankcase improves overall balance and handling and eliminates external oil lines.
Redesigned piston, crankshaft and connecting rod for increased performance and durability. An oil jet now directs oil at the piston bottom for increased cooling.
449cc five-valve DOHC liquid-cooled beast is still the most powerful thing in 250-Class MX.
39mm Keihin FCR flat-slide carburetor with throttle position sensor (TPS) and leak jet delivers precise fuel/air mixture and instant throttle response.
Revised CDI ignition keeps that amazingly broad and deep powerband hard-hitting, yet controllable.
Lightweight, titanium valves and load-reduced springs are super light, minimizing reciprocating mass for fast-revving, hard-hitting power delivery across the rev range.
Additional weight-saving engine features include: small-design cam chain tensioner and oil pump, aluminum oil hose, all-titanium exhaust header, flange, bracket and heat shield and light CDI ignition unit.
Primary kickstarting with automatic decompression and convenient handlebar-mounted hot start lever ensures easy restarts. A new kickstart lever provides efficient starting, hot or cold.
Kick pinion gear is separate from the primary driven gear for smoother clutch engagement.
More weight savings come via two-piece (part aluminum, part plastic) engine protector plates and thin-walled engine guard construction.
Removable aluminum rear subframe constructed of square-section pipe for light weight and easy maintenance.
Lightweight front wheel hub for reduced unsprung weight and increased durability.
Lightweight front and rear brake calipers with aluminum pistons and anti-bubble front master cylinder, 250mm front and 245mm rears discs, deliver strong stopping power with progressive feel.
Premium Dunlop knobbies provide unbeatable, competition-spec traction and great wear.
Lightweight 21-inch front and 19-inch rear Excel rims are exceptionally durable and reduce unsprung weight.
Additional Features:
“Gripper” style seat cover offers excellent feel and control.
Wide, cleated, folding titanium footpegs are light, strong, and provide excellent comfort, grip and ground clearance.
Trick, works-style clutch lever features oversize barrel adjuster for easy, on-the-fly adjustability of lever/cable play.
Cleated rear brake lever and folding shift lever tip offer superb grip and excellent durability.
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