Big light four-strokes are truly wonderful. What is not so wonderful is when they get a mind of their own and refuse to start. With the big-bore version WR of last year, this is one bike that really did not like to re-start after falling over on its side. So this year, it not only gets the coveted electric foot, it also got a bump up in displacement to match the cubes of the YZ.

Introducing the all-new WR450F, with more power, significantly reduced weight, a stronger chassis, smoother suspension, more aggressive bodywork, and a bunch of other improvements. The magic little trigger is merely the icing on this new trail missile. It has a larger 449cc four-stroke powerplant, stiffer, lighter-weight frame and swingarm, stronger brakes and a bunch other upgrades.

It's enduro-ready, with head and taillights, resettable tripmeter, large-capacity fuel tank, USFS-approved spark arrestor and race-spec Excel rims. Manufacturer's Suggested Retail Price...$6,399.

NEW FOR 2003

• Yamahas most advanced 4-stroke Enduro machine is stronger, lighter and better-handling, featuring all-new, super-easy electric starting!
  
• 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.
  
• Retooled carburetor features throttle cover with improved sealing and all-new hot start system with convenient, handlebar-mounted lever.
  
• Larger-capacity radiator and louvers ensures maximum cooling efficiency.
  
• Redesigned airbox features all-new retaining bracket for improved sealing.
  
• Super-strong twin-spar frame redesigned with reduced weight and greater lateral rigidity for minimal flex and sharp handling.
  
• All-new tapered swingarm features less weight and greater rigidity 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.
  
• New-design removable aluminum rear subframe reduces weight and allows easy maintenance.
  
• All-new, lighter-weight front and rear master cylinders and calipers, combined with 250mm fully floating front and 245mm rear disc, delivers 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:

• All-new automatic decompression system eliminates manual lever, ensuring easy restarts in any gear.
  
• Liquid-cooled, 449cc, 5-valve, DOHC, 4-stroke produces tremendous, hard-hitting low- and mid-range torque and a broader powerband tuned specially for enduro/off-road performance needs.
  
• 39mm Keihin FCR flat-slide carburetor with throttle position sensor (TPS) ensures ultra-precise fuel/air mixing and lightning-quick throttle response.
  
• Digital CD ignition system delivers more precise spark and monitors engine speed to ensure optimal timing for faster, stronger response during hard acceleration.
  
• Slick-shifting, wide-ratio, 5-speed transmission with YZ450F-spec, multi-plate clutch geared specially for quick-hitting power in woods and hard-pulling top-end on wide-open trails.
  
• Lightweight exhaust system maximizes engine power and allows hassle-free replacement of oil filter.
  
• Stainless steel muffler with USFS-approved spark arrestor resists corrosion.
  
• 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 with compression and rebound damping adjustability.
  
• Low-friction outer tubes and aluminum piston rods ensure smooth, compliant fork stroke for superior handling 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 21" front and 18 rear Excel rims provide exceptional durability and help reduce unsprung weight for optimal suspension performance.
  
• Premium Dunlop 739 knobbies offer competition-spec traction and excellent wear.

Additional Features:

• Endure-legal lighting front and rear increase versatility by maximizing nighttime and low-light visibility.
  
• Large, 2.6-gallon fuel tank ensures excellent range.
  
• Resettable tripmeter allows rider to keep track of both mileage and fuel reserves.
  
• Wde, cleated, folding cast alloy footpegs provide excellent comfort, grip and ground clearance.
  
• Adjustable front brake lever.
  
• Cleated rear brake lever and folding shift lever tip offer superb grip and excellent durability.
  
• Lightweight aluminum kickstand adds convenience and tucks up high when not in use.
  
• Team Yamaha-inspired two-tone (black/blue) seat.
  
• Repackable exhaust silencer.
  
• Durable, comfortable handlebar grips.
  
• Stainless steel clutch cable for longer life.

2003 WR450F Specifications:

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