2008 Yamaha WR250R and WR250X

Yamaha have launched the 2008 WR250R along with a WR250X supermoto version. The wet sumped, fuel injected engine features service intervals less demanding than the motocross four strokes.

Yamaha have launched the 2008 WR250R along with a WR250X supermoto version. The wet sumped, fuel injected engine features service intervals less demanding than the motocross four strokes. Full details from Yamaha follow below:

2008 Yamaha WR250R and WR250X

To say that the release of the WR250R represents the dawn of a new era is no idle boast, as magazine journalists discovered during the launch of the model in New Zealand’s South Island recently. In one fell swoop, the new model has carved out a fresh niche in the popular on/off road bike category.

The new category has been dubbed “Supertrail”, and as Trail Zone?s editor Andrew Clubb notes: “What sets the WR250R apart form the pack is the fact it combines the best of both worlds, by offering competition bike performance in a package that delivers everyday convenience both on and off the road. The WR250R represents the future of trail riding on a global scale.”

Yamaha has achieved this by designing the bike from the ground up to combine scintillating performance both on the dirt and the tar in a setup that doesn’t require the same high service requirements demanded by full enduro race spec motorcycles. Both motorcycles come with long service intervals and a two year warranty.

The WR250R (and WR250X Supermoto version) is powered by an all new fuel injected 250cc engine that meets the strictest emission laws slotted into a sweet hybrid steel/aluminium chassis that is equally capable on the road or in the bush. The liquid-cooled 4-stroke DOHC 4-valve engine has been built to deliver outstanding acceleration and instant response that exceeds anything ever offered in the 250cc single-cylinder street-legal category. It features the same big 77.0 mm bore and short 53.6mm stroke as Yamaha’s Grand Prix winning YZ250F motocrosser and WR250F enduro bikes.

The all-new short-stroke engine features a specially designed 4-valve cylinder head with a compact pent-roof combustion chamber which helps the WR250R deliver instant throttle response and remarkably strong performance right through the rev range to its maximum power output at 10,000 rpm. The 4-valve layout permits the use of a centrally-located spark plug for quicker ignition flame spread  and by offering a reduced surface area, the pent-roof combustion chamber allows more complete combustion of the fuel/air mix.

In order to achieve class-leading power output and outstanding response, the new cylinder head features a high 11.8:1 compression ratio, and utilises extra-large titanium intake valves which are of a relatively greater diameter than the exhaust valves compared to a traditional 4-valve design. In addition, the high-lift camshafts have been specially treated by our WPC (Wonder Process Craft) technique which involves spraying fine powder at a high speed to increase surface hardness and reduce frictional losses.

By optimising the complex relationship that exists between the size and number of valves, the valve skirt diameter, the valve seat angle and the camshaft profile, Yamaha’s engineers have succeeded in creating a new-generation lightweight 4-stroke single that is set to put the 250cc category back on the map. In order to achieve class-leading throttle response together with fuel economy and environmental responsibility, the new WR250R is equipped with a fuel injection system –  the first time this has been used on a Yamaha 250cc on-off road machine.

The compact ECU unit receives data from a crank sensor, intake air pressure sensor and throttle position sensor, allowing it to calculate the engine’s optimum fuel volume, intake air volume and injection timing. The fuel/air mix is fed to the 4-valve pent-roof combustion chamber via a long nozzle 12-hole two-directional injector with a wide timing range, and the highly detailed mapping of the fuel injection system ensures strong power delivery and instant throttle response right through the machine’s wide operating range.

Overall intake efficiency is greatly enhanced by the use of a new downdraft-type straight intake system. The use of this performance-boosting straight intake has been made possible by the adoption of a newly-designed rear suspension linkage which frees up space behind the engine. The intake is equipped with an air control valve, which, together with the EXUP system fitted to the exhaust, allows the ECU to accurately control the WR250R engine’s airflow from the intake right through to the exhaust.

Highly efficient heat dissipation is one of the key factors that allow the new WR250R to deliver consistently strong performance at high rpm. A lightweight forged piston runs in the plated cylinder, and this combination of a heat-resistant piston together with the high heat transmission rate of the plated aluminium cylinder ensure that the engine is able to deliver a consistently strong supply of power. In addition, the single radiator is equipped with a high-efficiency blower which maintains the system’s cooling function at lower speeds, and in doing so helps to achieve optimum power and reduced oil consumption.

By rearranging the relative positions of the crank shaft, main shaft and drive shaft and reducing the space between them  – partly due to the elimination of the kick starter -Yamaha designers have been able to minimise the engine’s physical dimensions and achieve a greater concentration of mass, resulting in highly responsive handling qualities. The new WR250R benefits from a wet-sump lubrication system which offers a number of advantages.

Because this system contains all the lubricating oil in an oil pan beneath the engine, there is no need for an external oil tank or reservoir, and therefore no external oil pipes are required. The wet-sump design also requires fewer parts and is lighter, and the absence of external oil pipes also enhances the overall aesthetics of the engine. Although the wet-sump design tends to be taller than its dry-sump counterpart because of the integral oil pan, the efficient design of the WR250R’s chassis has allowed the wet-sump to be accommodated between the tubes of the double cradle frame, thereby keeping engine height to a minimum, which allows for a generous 300mm of ground clearance.

Direct ignition coils are featured on the WR250R – the first time this advanced system has ever appeared on a Yamaha on-off road machine. This compact system incorporates a booster in the spark plug cap, and eliminates the need for a frame-mounted ignition coil – as well as helping to reduce weight and free-up space above the engine. Yamaha’s engineers have pursued virtually every possible solution in order to reduce the overall dimensions of this advanced 250cc 4-stroke engine, and the use of a YZF-R series type rare-earth type AC magneto is another example of space-saving technology.

The use of fuel injection places greater demands on a machine’s electrical supply system, and this would typically require the fitment of heavier components to generate the greater capacity. However, by using elements such as neodymium (Nd) in place of the traditional ferrite materials, it is possible to create a particularly small and powerful AC magneto which offers increased electrical power with reduced size and weight. Yamaha’s engineers have spent a great deal of time in creating a highly efficient smooth-action clutch which allows the rider to utilise the new engine’s performance to its full potential.

Featuring an optimised stroke length, and equipped with thirteen compact plates (seven friction plates and six clutch plates), the WR250R?s clutch requires only a light lever load in order to slip the clutch when pulling away or exiting corners. The combination of the smooth-action clutch and high-performance short-stroke engine makes for a lively and exhilarating ride. To help minimise overall weight, the new WR250R is equipped with a compact and efficient electric starter, while the kick starter has been eliminated.

An auto-decompression function makes for easy starting with the push of a button, and for additional reliability the starter link features a torque limiter. The WR250R’s 6-speed transmission has been specially developed to optimise the power characteristics of the new high-compression short-stroke engine. The ratios have been carefully selected to deliver impressive performance and strong driveability in a wide variety of situations, from city streets through to twisty trails and fast dirt tracks.

And for increased durability the new transmission benefits from a shower-type lubrication system which ensures good gear lubrication and smoother shifting. Overall exhaust efficiency is enhanced by the use of a new 3-stage expansion-type muffler which is located close to the machine’s centre of gravity in order to ensure lighter handling performance.

For even lower emissions the new WR250R is equipped with an oxygen sensor in the exhaust which feeds data to the ECU and adjusts fuel/air mix accordingly to ensure more complete combustion. In addition, an air induction system introduces air into the exhaust to re-burn any uncombusted fuel that is detected, and finally, the exhaust gases are cleaned by a honeycomb-type catalyser to reduce emissions even further.

The WR250R/X features the first 3-section semi-double cradle frame ever used on a Yamaha on-off road model. This advanced new semi-double cradle frame has been developed using a great deal of the technology featured on our race-winning YZ250F motocross bike and the WR250F enduro machine, and consists of a cast aluminium/forged aluminium main frame, steel down tube and steel subframe.

The main frame features cast aluminium components for the front and rear sections, with forged aluminium parts for the other areas, and these are welded together to create an extremely light and enormously strong unit. Manufactured from thin-walled 25.4mm diameter steel pipe, the high-tensile single downtube offers a number of advantages over a conventional design. Firstly, by being a separate component it facilitates engine mounting during manufacture, and secondly, this design helps to achieve the desired ground clearance with the new wet-sump engine.

By using a combination of cast and forged aluminium for the main frame as well as a high-tensile thin-walled steel downtube and a steel subframe, the WR250R’s new 3-section semi-double cradle frame delivers an idealised balance of strength and rigidity for lightweight manoeuvrability, quick turning and agile handling. Virtually every aspect of the WR250R has been designed and manufactured to an advanced competition-type specification, and this commitment to high quality components can also be seen in the new aluminium swinging arm.

Like the main frame, the innovative new swinging arm utilises a special combination of aluminium components in order to achieve the desired balance of strength and rigidity, and its low unsprung weight also ensures improved rear suspension performance. The cross member is manufactured from cast aluminium, while the left and right arm sections are extruded aluminium, and the end pieces are forged aluminium. To achieve the optimum weight/rigidity balance and also enhance the bike?s aggressive cutting-edge styling, the new lightweight swinging arm features an asymmetrical cross section.

To complement the advanced new 3-section frame, the WR250R is equipped with a high-specification suspension package which has been designed to be able to handle a diverse range of on and off road riding conditions. At the front end the WR250R is fitted with race-quality upside-down front forks offering a generous 270mm of travel, and equipped with flex-resistant 46mm tubes which deliver a good balance of rigidity. Like our motocross and enduro bikes, the WR250R?s forks feature lightweight aluminium triple clamps – cast aluminium for the handlebar crown and forged aluminium for the under bracket – and aluminium is also used for the steering shaft in order to minimise weight for responsive steering.

These 46mm diameter forks offer a full range of adjustability for preload and rebound/compression damping, and with a fork offset of 25mm and axle offset of 28mm, this high quality front end delivers neutral steering, excellent shock absorbing performance, and outstanding running stability on the road and in the dirt. The race-bred link-type rear suspension system has been developed using the knowledge gained from our World Championship motocross and enduro teams, and is one of the most advanced in the class.

The lightweight aluminium swinging arm operates a new shock featuring a 14mm diameter rod and large-capacity 46mm diameter cylinder which has been designed to handle everything from dirt roads through to extreme off road conditions. Like the front forks, the rear shock is fully adjustable for preload and rebound/compression damping, and offers 270mm of wheel travel, giving high levels of rider comfort in a wide variety of conditions both on and off the road.

Race-developed technology is evident wherever you look on the new WR250R, and another example of the close relationship between this new 250 and our race bikes can be seen in the wave-type 250mm front and 230mm rear discs. This design is used on our factory race bikes and also on our production YZ and WR models, and helps to reduce unsprung weight, as well as assisting in clearing any debris from the brake pads.

The WR250R’s instrumentation has been designed to offer good levels of visibility and operability, while also being light and compact. The basic mode display includes a speedometer, clock and tripmeter, while the measurement mode includes a stopwatch and distance-compensation tripmeter. Yamaha’s designers have concentrated their efforts on ensuring that weight is kept as low as possible, and that there is also a good concentration of mass.

This has been achieved by using lightweight and compact components wherever possible – such as the rare-earth AC magneto and direct ignition coil. In addition, the new muffler has been positioned close to the machine?s centre of gravity, and the size and weight of the front and rear fenders and sidecovers has been minimised to help concentrate the machine’s mass. The handlebar/seat/footrest relationship has been carefully chosen in order to create a comfortable yet effective, upright riding position which makes the rider feel at one with the machine.

The slim steel fuel tank offers excellent knee grip, and the frosted-finish competition-style seat allows easy weight shifting when riding off road. And with its 930mm seat height and 300mm ground clearance, the exciting new WR250R is ideally suited to challenging off road conditions. WR250X features Featuring the same advanced technology as the WR250R, the all-new WR250X has been developed to offer quick changes of direction, high levels of traction during cornering, great stopping power and a lower seat height for good controllability in urban situations.

The supermoto-style WR250X runs with 17-inch front and rear wheels equipped with a 110mm wide front tyre and 140mm wide rear tyre featuring a radial construction. The radial tyres deliver lower rolling resistance and high levels of traction for remarkable roadholding qualities, making the WR250X an amazingly agile and responsive machine in the urban environment. To accommodate the different size and handling characteristics of the wide radial tyres, the WR250X runs with revised suspension settings at the front and rear.

The WR250X front forks utilise stiffer springs and run with different damping settings in response to the pure street usage of the machine – as well as to handle the increased braking power of the new front disc. Meanwhile the rear suspension has also been modified with revised damping settings and a stiffer spring – and in order to achieve a 35mm reduction in seat height for improved controllability, the WR250X features a slightly shorter rear shock absorber.

These changes to the suspension perfectly complement the handling characteristics of the new radial tyres and 17-inch wheels to create a sharp-handling machine which offers new levels of cornering potential, together with remarkable overall agility and breathtaking directional changes.

WR250R/X SPECIFICATIONS

Engine
Engine type Liquid cooled, 4-stroke, DOHC, 4-valve,
forward inclined single cylinder
Displacement 250 cc
Bore x stroke 77.0 X 53.6 mm
Compression ratio 11.8:1
Lubrication Wet sump
Fuel System Electronic fuel injection
Clutch type Wet, multiple-disc coil spring
Ignition system TCI
Starter system Electric
Transmission Constant mesh, 6-speed
Final transmission Chain
Fuel tank capacity 7.6 L
Oil tank capacity 1.5 L

Chassis
Chassis: Semi double cradle
Front suspension Telescopic forks
Front travel 270 mm
Rear suspension Swingarm (link suspension)
Rear travel 270mm
Front brake Single disc, Ø 250mm / Ø 298mm
Rear brake Single disc, Ø 230mm
Front tyre 80/100-21M/C 51P / 110/70R 17M/C 54H
Rear tyre 120/80-18M/C 62P / 140/70R 17M/C 66H

Dimensions
Length 2180mm / 2115mm
Width 810mm
Height 1230mm / 1190mm
Seat height 930mm / 895mm
Wheel base 1420mm / 1425mm
Min grd clear 300mm / 265mm
Dry weight 126kg / 128kg

RRP (inc GST) $9999 / $10,399
Warranty 24 months, unlimited kms, parts and labour
Colours Racing Blue or Sports White / Sports White
or Yamaha Black