Introducing the all-new, all-powerful, all-light YZ450F.

Yamaha forged a totally new machine from the Dunlops up. With features like an all-new, liquid-cooled, 5-titanium valved 449cc single, with a completely redesigned automatic decompression system for easy-starting. An all-new 4-speed transmission and a beefed up clutch with larger, stronger plates.

Lighter weight frame and swingarm. Completely revised suspension, stronger brakes and more aggressive ergos and styling. And its incredible weight loss makes it harder-hitting and sharper handling than ever.

The 2003 YZ450F. The new four-stroke standard-bearer has arrived.

ALL-NEW FOR 2003:

• The industry's most powerful and most advanced 4-stroke MX machine returns stronger, lighter (by over 10+ pounds!) and better-handling than ever!
• All-new, liquid-cooled, 449cc, 5-valve, DOHC, 4-stroke with titanium valves features longer 63.4mm stroke (up from 60.1mm) and completely new-design cylinder head, piston and crankshaft, delivering flatter, broader torque (for instant hook-up) with higher over-rev capacity and crisper, more linear throttle response.
• Cylinder head is smaller in design for reduced weight.
• All-new, lighter-weight crankshaft helps decrease inertial mass by 20%, reducing friction for faster-revving low-rpm response.
• New-design piston features shorter skirt and smaller pin boss diameter to help reduce weight.
• Shorter, lighter-weight titanium valves and load-reduced springs are nearly 20% lighter, further reducing reciprocating mass for faster-revving, harder-hitting power delivery across the rev range.
• Additional weight-reducing engine upgrades include: smaller-design cam chain tensioner and oil pump; aluminum oil hose (was steel); all-titanium exhaust header, flange, bracket and heat shield; and lighter CDI ignition unit, coil ad magnet rotor.
• Improved carburetor features throttle cover with excellent sealing and all-new hot start system with convenient, handlebar-mounted lever.
• All-new automatic compression system eliminates manual lever, ensuring easy restarts in any gear.
• Redesigned airbox features all-new retaining bracket for improved sealing.
• All-new, smooth-shifting 4-speed transmission sheds one gear to help reduce weight, while revised 1st, 2nd and 4th gear ratios delivers new engine's potent powerband to the ground with maximum efficiency and hook-up.
• Super-strong frame redesigned with reduced weight and greater lateral rigidity for minimal flex and razor-sharp handling.
• All-new tapered swingarm features less weight and greaterrigidity for more compliant rear suspension action.
• Recalibrated front fork settings deliver improved damping force with less bottoming for a smoother, more compliant overall stroke.
• Rear shock refinements include improved actuation, a new linking ratio and enhanced damping force.
• Removable aluminum rear subframe redesigne, reduces weight and allows for easy maintenance.
• All-new, lighter-weight front and rear master cylinders and calipers, combined with 250mm fully floating front and 245mm rear disc, deliver stronger stopping power with greater, more progressive control and feel.
• Retooled steering crown combines with all-new bodywork - flatter seat, fuel tank and radiator shrouds - creates a more aggressive riding position while allowing optimal rider movement.
• More weight savings come via all-new, two-piece (part aluminum, part plastic) engine protector plates and thinner-walled engine guard construction.

Engine:

• 39mm Keihin FCR flat-slide carburetor with throttle position sensor (TPS) delivers ultra-precise fuel/air mixing and instant throttle response.
• Digital CD ignition system delivers ultra-precise spark and timing for faster, stronger engine response during hard acceleration, and less kickback during starting.
• Large-capacity radiator provides outstanding cooling efficiency.
• Primary kickstarting (with all-new automatic decompression and hot start lever) ensures easy restarts.
• Trick, works-style clutch lever features oversize barrel adjuster for easy, on-the-fly adjustability of lever/cable play.

Chassis/Suspension:

• Removable aluminum rear subframe constructed of square-section pipe for reduced weight.
• Lightweight 46mm inverted Kayaba cartridge fork features 11.8" of travel and compression and rebound damping adjustability.
• Low-friction outer tubes and aluminum piston rods ensure smooth, compliant fork stroke and light steering.
• Rear suspension system features fully adjustable Kayaba shock with 12.4" of travel and separate adjusters for high- and low-speed compression damping.
• Lightweight front wheel hub reduces unsprung weight and increases durability.
• Premium Dunlop 739 knobbies offer unbeatable, competition-spec traction and excellent wear.
• Lightweight 21" front and 19" rear Excel rims are exceptionally durable and reduce unsprung weight.