Most eagerly awaited bike of the year is a big claim. But when that statement refers to Australia's best selling motorcycle which is all new for 2007, it's more than a claim. It's for real.

Yamaha has raised enduro machine design to the next level with the introduction of the WR450F. Featuring the most advanced, cutting-edge engine and chassis technology ever seen on a Yamaha enduro machine, this all-new motorcycle offers today's off road rider a very real advantage at every level.

A new lightweight aluminium semi-double cradle frame carries a reliable high performance engine that delivers increased levels of useable power in a high-tech package topped off with totally new ergonomic bodywork.

The 2007 Yamaha WR450F is an all-new pure enduro machine which is designed to offer the serious competitor and discerning off road rider an even higher level of engine and chassis performance, combined with unrivalled reliability and outstanding quality.

Yamaha has been at the forefront of enduro machine development for many years, and our international and national team riders have ensured that Yamaha WRF models have established themselves as the main contenders at every level.

Now we are taking enduro machine design to another level with the most advanced 450cc 4-stroke of the decade. The all-new WR450F features a new high-performance DOHC 5-valve engine that is tuned to deliver remarkably strong power in the low to mid range, giving winning performance over a wide variety of terrain. For 2007 this high-tech 450 is also equipped with a new aluminium chassis which has been developed to offer an idealised rigidity balance for quick directional changes in the tight stuff and winning times in the MX tests.

From its specially developed wide ratio transmission through to the high quality precision-machined components - and thoughtful details such as the quick-release air cleaner cover - every single feature on this new enduro machine is designed to allow enduro racers and recreational off road riders to discover a new dirt riding experience, and encourage them to discover their true riding potential.

WR450F ENGINE

The base design for the 2007 WR450F is the latest generation DOHC 5-valve YZ450F engine, which also forms the basis for the MXGP-winning YZ450FM campaigned by MX1 multi World Champion Stefan Everts.

The winning performance of the YZ450F is on record for all to see, and armed with one of the most successful MX engines available today, Yamaha's engineers have considerably reworked the base design to suit the specific requirements of today's enduro rider.

This highly advanced engine features a wide range of special modifications which are designed to ensure that the all-new WR450F establishes itself as the leading choice with serious enduro riders and also with recreational off road riders who demand high performance, class leading quality and cutting edge design.

The new WR450F engine is equipped with a new tungsten balancer mounted on durable ball bearings which helps reduce vibration and makes for a smoother and more direct throttle response. To match the new enduro balancer the new WR's crank mass has been optimised, and a high strength piston and connecting rod are featured.

By helping to reduce vibrations and deliver a more rider-friendly power delivery, the combination of a new balancer and revised crank mass helps to reduce fatigue and therefore enhance a rider?s competitiveness in enduros and cross country events.

Every experienced enduro rider knows that it is not simply outright power that makes an enduro bike a winner - it is the quality and character of the power that matters above all else.

For this reason Yamaha's engineers have optimised the cam profiles and timing on both the inlet and exhaust side to maximise the new WR450F?s performance in the typical enduro machine engine speed range. These important changes to the camshaft design on the 449cc DOHC engine gives a significant torque boost in the low to mid speed range, thereby ensuring that the new WR450F is ideally suited to riders of all abilities.

Revised carburettor settings are used on the new engine to complement the changes made to the new inlet and exhaust camshaft timing. The new settings are designed to optimise the performance gains made in the crucial low to mid speed range, and give a smooth throttle response throughout the new engine?s wide operating range.

A new exhaust system has been fitted to the 2007 WR450F to match the revised camshaft timing. The new system features a longer and smaller diameter exhaust pipe with a shorter silencer, which is mounted in a lower, more forward position. These changes help to enhance the low to mid range performance gains made by the new camshaft design, and also help to give a better concentration of mass for enhanced handling qualities.

Compared to the YZ450F base engine, the 2007 WR450F incorporates a revised primary reduction ratio as well as a new wide ratio five speed transmission. The gear ratios have been carefully chosen after exhaustive testing by our European test riders, and this new wide ratio transmission optimises the bike's increased low to mid-range performance.

The WR features a new dry sump lubrication system which is designed to ensure highly efficient lubrication whilst also helping to concentrate mass. This system is the same as that used on the YZ450F, and features a new oil tank contained within the front of the crankcases which carries the oil much lower than the previous oil-in-frame system.

This innovative design eliminates the need for external oil pipes which previously connected the engine with the frame-mounted oil tank. The advantages of this design include higher reliability, and increased mass centralisation for lighter handling feel.

Other new features on the engine include a new oil cooling spray directed at critical points in the cylinder for enhanced piston cooling, and a new internal cylinder head oil-way feeding the camshafts, which eliminates the need for an external pipe.

Another significant change which has been introduced to optimise the new bike's centre of gravity is the adoption of a more upright cylinder angle. This detail change - which is not that obvious to the naked eye - helps to create an optimum weight balance, that, combined with the new aluminium frame, makes for a lower centre of gravity and a lighter handling feeling.

To match the increased engine performance, the new WR is equipped with new design YZ-type radiators offering an increase in frontal area for improved cooling efficiency. The new radiators also benefit from the addition of new reinforcement brackets which are designed to increase their rigidity for improved durability, and new style louvred panels which give efficient airflow into the radiators are featured.

The 2007 WR450F benefits from a new intake layout which is designed to accommodate the all-new aluminium frame. Also new is a redesigned air box featuring a new quickly detachable cover for simpler air filter maintenance.

2007 WR450F Engine Technical Highlights

• 449cc 4-stroke liquid-cooled
• DOHC 5-valve
• Bore x stroke 95.0mm x 63.4mm
• Electric start
• Based on latest generation YZ450F design
• Enduro balancer mechanism
• Optimised crank, con rod and piston
• Special WR camshaft profile and revised inlet/exhaust timing for stronger low to mid range performance
• Revised carburettor settings
• New design exhaust system
• Wide ratio 5-speed transmission
• New dry sump lubrication for optimised mass concentration
• More upright cylinder angle
• Large capacity reinforced radiators
• Revised intake layout
• New compact AC Magneto assembly

WR450F CHASSIS

The 2007 WR450F's new lightweight aluminium semi-double cradle frame is based on the YZ450F design, and is one of the most advanced in the off road world. Unlike some other aluminium frames, the WR450F?s semi-double cradle frame offers a lower centre of gravity than the beam-type off- road frame design, and can also be constructed using fewer components.

The Yamaha semi double cradle frame has been manufactured using three types of aluminium - cast, forged, and pipe/extruded - that has enabled our designers to build in an optimum balance of rigidity.

Forged aluminium is used for the upper portion of the main tube as well as the dividing point of the cradle, and around the swingarm pivot. Cast aluminium is used at the head tube and parts of the main frame. Aluminium pipe is used for the under loop - and extruded aluminium is used at the swingarm pivot.

This sophisticated frame consists of just nine components welded together using Yamaha-exclusive technology to create a single unit offering the right amount of 'forgiveness', and a low centre of gravity. Unlike weight or horsepower, forgiveness is difficult to quantify, and yet it is a crucial quality that has a major influence on the handling characteristics of every dirt bike.

The actual level of the balanced rigidity that is engineered in to the WR frame has been arrived at after many thousands of hours of real world testing by our development riders. Yamaha's previous steel framed WR's were rightly praised for their superb handling characteristics thanks to their idealised rigidity balance, and the new generation aluminium frame fitted to the WR450F is once again ready to set new standards.

In the same way that the character of a machine's power is just as important as its maximum power output, so too is a machine's weight distribution just as significant as its overall weight. Whereas an off road beam frame tends to concentrate much of its mass high up on the machine, the Yamaha semi-double cradle design has much of its mass low down. This feature, combined with the new low centre of gravity dry sump engine, ensures that the new WR450F delivers lighter feeling handling performance.

The new frame's balanced rigidity or 'forgiveness' - combined with the inherently low centre of gravity of a semi-double cradle layout - makes for a class leading ride quality that translates into winning handling performance for the enduro racer, and class leading comfort for the recreational dirt rider.

For optimum rider control in various situations the WR450F features a number of enduro-specific dimensions compared to the YZ450F, including a lower seat height, and lower footrests position. The stainless steel footrest design is new for 2007, and features a 11.2mm wider front-to-rear dimension for reduced pressure on the rider's soles - a detail that can make the difference when you're on the bike all day.

Combined with the low centre of gravity and balanced rigidity chassis, these detail changes make for lighter feeling handling qualities, notably in tight, woody terrain where lock-to-lock slow speed turns are often experienced.

In keeping with its all-new engine and chassis, the 2007 WR450F features completely new bodywork which includes an 8-litre fuel tank with YZ-style shrouds, a compact new 35/36.5W headlight, new side covers and rear fender, and a lightweight LED rear light assembly.

Although the seat is mounted lower than on the YZ, the WR450F seat is actually thicker and is manufactured using more comfortable foam for improved comfort. We have also paid particular attention to the area where the front of the seat meets the 8-litre fuel tank in order to enable easy weight shifting when approaching corners.

A new one piece plastic wrap-around resin engine guard is 80g lighter than the previous three part aluminium design, and is easily removed by undoing just three bolts. The ultra-light design offers greater protection to the underneath and sides of the crankcases, and also helps to prevents mud buildup under the new engine.

The new air cleaner box can be opened with the release of a single fastener, and this feature, together with a quick-release air filter mechanism, makes for easy filter changes whether you?re in the workshop or the parc ferme.

New Pro Taper aluminium handlebars help to keep weight to a minimum and underline the attention to detail on this high quality enduro bike. Offering a better riding position, these Pro Taper bars are just one example of the wide range of high quality components that mark the 2007 WR450F out as one very special dirt bike that is ready for anything, straight out of the crate.

For the first time on a WR model, the new WR450F comes equipped with lightweight wave type front and rear disc brakes which reduce unsprung weight by 80g and offer improved braking and pad cleaning performance.

More weight is saved by the use of forged upper and lower triple clamps which grip the 48mm front forks. Also new are forged handlebar clamps, and this significant reduction of weight - which is situated high up on the steering assembly - helps to accentuate the light steering feel of the new WR.

A new rear shock is equipped with a larger sub tank, and overall length is increased to give stable performance over longer periods, while the 48mm front forks run with revised enduro-specific settings to match the new aluminium chassis.

In common with the 2007 YZ, the new WR450F is equipped with a range of ultra light components, including a new rear axle, chainguard, chain slipper and a variety of lightweight nuts and bolts.

Other important features include the forged aluminium sidestand, 18-inch rear wheel, enduro silencer, O ring chain and a new more compact 536cc catch tank. The 2007 model also features a new compact new digital speedometer.

2007 WR450F Chassis Technical Highlights

• New lightweight aluminium semi-double cradle frame
• Special WR dimensions and new footrests
• New generation YZ-style bodywork
• Special WR seat
• Wrap-around plastic resin engine guard
• New air cleaner box
• Pro Taper handlebars
• Wave type discs
• Lightweight forged triple clamps
• Uprated rear suspension
• Lightweight components
• 18 inch rear wheel
• Forged aluminium sidestand
• 536cc catch tank
• Enduro silencer
• O ring chain
• Compact digital speedometer
• New graphics

Sean Hawker, advertising and PR co-ordinator
Yamaha Motor Australia,
489-493 Victoria Street, Wetherill Park, NSW 2164
Office: (02) 9757 0068 Mob: 0438 423844 Fax: (02) 9757 1384
Website: www.yamaha-motor.com.au