REVIEW: 2007 YAMAHA ENDURO MODELS

Featuring the most advanced cutting-edge engine and chassis technology ever seen on a Yamaha enduro machine, our all-new 2007 models offer today’s enduro rider a very real advantage at every level.

Both the WR450F and WR250F run with a new lightweight aluminium semi-double cradle frame and are driven by new high performance engines that deliver increased levels of useable power – and these advanced high-tech packages are completed by totally new ergonomic bodywork.

With these completely redesigned enduro models, Yamaha believe that we now offer the most complete and most advanced 4-stroke enduro bikes in their respective classes.

NEW WR450F

The all-new E2 class leader

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

All-new YZ-based 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.

Enduro balancer and optimised crank, con rod and piston

Enduro riders are in the saddle for many hours, and so 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.

Special WR cam profiles and timing for stronger low to mid range performance

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

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.

New design exhaust system

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.

Wide ratio 5-speed transmission

Compared to the YZ450F base engine, the 2007 WR450F incorporates a revised primary reduction ratio as well as a new wide ratio 5 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.

New dry sump lubrication for optimised mass concentration

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 oilway feeding the camshafts, which eliminates the need for an external pipe.

More upright cylinder angle

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.

Large capacity reinforced radiators

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.

Revised intake layout

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

2007 WR450F Engine Technical Highlights
450cc 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

New lightweight aluminium semi-double cradle frame

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.

 

2007_wr450f_frame

 

 

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.

Special WR dimensions and new footrests

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 in the saddle 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.

New generation lightweight YZ-style bodywork

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.

Special WR seat

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.

Wrap-around plastic resin engine guard

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 build-up under the new engine.

New air cleaner box

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.

Pro Taper handlebars

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.

Wave type discs

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.

Lightweight forged triple clamps

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.

Uprated rear suspension

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.

Lightweight components

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 enduro-specific features

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 Highlight

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

Next: 2007 WR250F……

NEW WR250F

The record shows that the WR250F is the most successful 250cc 4-stroke enduro machine ever built, with four consecutive world titles. Its performance at world, national and local level underlines not only how good this bike is, but also how it can be a winner – whether ridden by a factory pilot or club rider.

This is undoubtedly the reason that so many riders of all abilities have chosen the WR250F time after time – and why so many riders have come back to it after trying something else.

 

 

The new 2007 model is designed to offer even stronger engine and chassis performance, while retaining the bike’s legendary rideability, or to put it another way, its rider friendly character.

High technology and impressive specifications on their own don’t win enduros or make for a great bike. It’s the way that the engine delivers its power and the manner in which the chassis handles everything from sandy whoops through to rutted forest tracks that counts.

In developing the new WR250F, Yamaha’s engineers have set out to create a machine that functions as one unit, and which responds to the rider’s inputs, rather than being a machine that is in control of the rider. The new YZ250F-derived powerplant brings higher levels of performance to the category, while the completely new aluminium semi-double cradle frame and ergonomic bodywork show that we’ve never been more serious about retaining our position as the leading 250 4-stroke manufacturer. And to administer the coup de grace to the opposition the new WR250F comes with aggressive new bodywork that complements its new high performance engine and lightweight aluminium chassis.

 

WR250F ENGINE

Yamaha’s domination of the MX2 World Championship in 2005 underlined just how competitive the 250cc DOHC 5-valve engine can be at the very highest level. So when we set out to create an all-new WR250F which would out perform the opposition, we decided to use this winning 4-stroke engine as the basis for our new generation enduro bike.

 

 

As with the new WR450F, the WR250F engine has been completely reworked in order to ensure class-leading engine performance in the extremely wide range of operating conditions associated with enduro competition.

WR-specific cam profile with optimised timing

The new WR250F’s liquid cooled DOHC 5-valve engine is equipped with revised camshaft profiles to enhance the bike’s low to mid range performance, the very place where enduro riders need to have the edge. No one wins by being fastest along the fire road – it is in the 2nd and 3rd gear going where the advantage is often gained, and the new WR250F delivers the right kind of power just when you need it.

Closer ratio transmission

As well as revised cam profiles, we’ve also revised the intake and exhaust cam timing for increased low to mid range flexibility, and to match these changes we have also equipped the new 2007 WR250F with a closer ratio transmission. The step between 3rd, 4th and 5th gear ratios is reduced to minimise the rpm reduction when shifting up, allowing the rider to stay within the optimum rpm range. These significant changes deliver increased punch right where it matters most, giving the WR250F rider a real and distinct advantage.

New dry sump lubrication system

The new engine is equipped with a new dry sump lubrication system featuring a compact 720cc oil tank located in front of the engine. This design helps to centralise mass for lighter feeling handling performance compared to the 2006 model.

In addition to these external changes the new engine incorporates a reshaped strainer compartment in the crankcase, giving a better oil circulation route, and the new strainer design increases crankcase volume, thereby reducing oil agitation resistance to give enhanced performance.

Larger reinforced radiators

To handle the increased engine performance and ensure stable running over longer periods, the 2007 WR250F runs with larger radiators offering a greater frontal surface area. These highly efficient radiators are also fitted with lightweight reinforcement brackets that increase the system’s rigidity for improved durability in the event of a fall.

New exhaust system

To accommodate the new aluminium frame design and also match the revised camshafts and timing, the exhaust system features a longer, smaller diameter pipe and a shorter silencer mounted further forwards.

Revised carburettor and CDI settings

To match the new cam timing the WR250F runs with revised carburettor settings and a new CDI with modified ignition mapping.

 

2007 WR250F Engine Technical Highlights
250cc 4-stroke liquid-cooled

DOHC 5-valve

Bore x stroke 77m x 53.6mm

Electric start

Based on YZ250F design

Special WR cam profile and timing for stronger low to mid range performance

Revised carburettor and CDI settings

New design exhaust system

Revised 5-speed transmission with closer 3rd, 4th and 5th gears

New dry sump lubrication with front mounted external oil tank for optimised mass concentration

Large capacity reinforced radiators

Revised intake layout

 

WR250F CHASSIS

Please note that the 2007 WR250F features the same chassis specification as the 2007 WR450F. Please refer to the ‘WR450F CHASSIS’ section for full details.

2007 WR250F 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

 


 

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