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| | | First Look : 2008 Yamaha WR250X, School of drift |  Written: 12/09/2007 : 11:36. Read 42060 times (27/day). | New bike in the Supermoto range, here is the Yamaha WR250X. Small Supermoto presented to be very fun but most of all easy! Light and nimble this WR250X will be, without a doubt, a real pleasure factory...
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At Yamaha it seems that they don't like compromises, and the aim of this WR 250X are just put aside the R1 model aim...
« No-compromise, highly-focused machines that offer riders a new level of engine and handling performance. »
To convince you here is a piece of the development goals :
Aggressive supermoto performance
New levels of agility and cornering performance
Race-bike performance and user-friendly features
Environmentally responsible low-emission engine
Fresh and aggressive styling
This new bike is also a Enduro Model called WR250R, for those who wants to take a ride in the fields and gravel roads... nice to begin or just to have fun without fear...
WR250 Engine
The WR250R is equipped with a newly-designed engine, a compact liquid-cooled 4-stroke DOHC layout running with 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 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.
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.
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 which enables the new WR250R. A lightweight forged piston runs in the plated cylinder.
In addition, the single radiator is equipped with a high-efficiency blower which maintains the system’s cooling function at lower speeds
Compact 3-axis layout
Using experience gained in the design of World Championship-winning motocross and enduro engines, Yamaha’s engineers have created an extremely compact 3-axis layout for the new WR250R powerplant. 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 have been able to minimise the engine’s physical dimensions and achieve a greater concentration of mass.
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.
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.
WR250 Chassis
The WR250 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 WR250’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 WR250 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.
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.
At the front end the WR250 is fitted with race-quality upside-down front forks fully adjustable 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 WR250’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.
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 cobbled city streets 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.
For the Supermoto Version WR250X, the chassis of the WR was « Supermotoised »...
With 17inches wheels, suspensions set as well, and tyres of 110 at the front and 130 at the rear.
A configuration that will give to the WR a very nimble behaviour in urban environment but also in twisty roads. Yamaha set suspensions more harder on the X so it will be more stable also...
To stop the « beast » Yamaha featured it with a 298mm front disc wave type with two pot caliper. Enough to stop the 128Kilos of the Yamaha if we add a 230mm wave disc at the rear...
A bike that will certainly be a great motorcycle for learner of Supermoto, the school of drift is open!
Chassis highlights WR250
Chassis
3-section semi-double cradle frame
Frame uses cast aluminium, forged aluminium and steel pipe
Lightweight aluminium swinging arm with asymmetrical cross section
46mm upside down forks with 270mm travel
Link-type rear suspension with 270mm travel
300mm ground clearance
Upright seating position offering optimum rider manoeuvrability
Tall 930mm seat height for effective off road performance
Multi-function digital instrumentation
Lightweight bodywork with excellent mass concentration
Wave type 250mm front disc and 230mm rear disc
LED tail light
Available colours
Sports White
Racing Blue
WR250X Technical Highlights
17-inch front and rear wheels
Stiffer front and rear suspension springs, revised damping settings
Larger diameter 298mm front disc brake
Lower 895mm seat height
Revised secondary reduction ratio (WR250R= 43/13; WR250X= 42/13)
Compact and aggressively-styled supermoto bodywork
Available colours
Yamaha Black
Racing Blue
Technical Specifications Yamaha WR250X
Engine
Type Monocylinder four strokes, double over head cam, four valves
Liquid cooled
Displacement 250 cm³
Bore x Stroke 77,0 x 53,6 mm
Compression Ratio 11,8 : 1
Max Power 22,6 kW (30,7 ch) à 10 000 tr/min
Max Torque 23,7 Nm (2,42 kg-m) à 8 000 tr/min
Lubrication Wet Sump
Fuel system Electronic Injection
Clutch Multiplate in oil bath
Ignition TCI
Starting Electric Starting
Gear Box six speed
Final Drive Chain
Fuel Tank 7,6 litres
Oil Tank 1,5 Liters
Chassis
Frame semi double cradle
Front suspension USD Fork
Front wheel travel 270 mm
rearsuspension Swingarm (monocross)
Rear wheel travel 265 mm
Front Brake Simple disc, Ø 298 mm
Rear brake Simple disc, Ø 230 mm
Font tyre 110/70R17M/C 54H
Rear tyre 140/70R17M/C 66H
Dimensions -
Overall lenght 2 115 mm
Overall width 810 mm
Overall height 1 190 mm
seat height 895 mm
Wheelbase 1 425 mm
Ground clearance 265 mm
Dry weight 128 kg
From a Yamaha press release
Aurélien Filippi
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