The new 2010 YZ250F –
Designed for the ultimate cornering performance
The YZ250F – proven in MX2 GP
The demands of a rigorous sport like motocross mean that any motorcycle is pushed to the extremes of reliability and efficiency. In this tough and exciting world of racing, Yamaha’s YZ250F set a new standard, and raised the technical level of how individuals can influence their off-road riding. Since its inception in 2001 and subsequent introduction to FIM World Championship competition in 2003, the YZ250F has set the benchmark for the four-stroke technology current seen on circuits today. Motocross legend Stefan Everts dominated the second half of the 2003 125 campaign, and in the following five years the bike helped 7 riders to their maiden victories - including two world titles earned by the spectacular Antonio Cairoli. The YZ250F is just as incisive today, with youngsters as Zach Osborne and Loic Larrieu displaying their talents in MX2-GP, and Christophe Charlier currently dominating the European MX2 Championship. Developed from this impressive racing heritage, the 2010 YZ250F is moving the four-stroke 250cc machine into the next phase of optimum track performance. It remains the wisest and best-equipped choice for youth riders aspiring to success on the track.
Cornering: the key to faster lap times
The Yamaha competition development team knows that Motocross races are won or lost in the corners. Riders are looking for a bike that will let them turn in earlier, and get on the gas sooner. That’s why, from the ground up, the YZ250F has been designed for exceptional cornering performance and better engine control. This couldn’t come from a quick fix, but only by developing the engine, chassis, suspension and other components together.
Technical highlights
Chassis and styling
· New design Bilateral Beam aluminium frame
· Revised caster and trail
· Front suspension with further maturation
· Rear suspension spring position optimised
· New-design flat seat
· New design fuel tank
· New lightweight parts
· New body styling with smaller-surface exterior parts
· Second colour, Competition White, offered (not available in all territories)
Engine
· Refined engine with refined character
· Aluminum retainer and low weighted valve spring
· New carburettor settings and funnel shape
· Modified exhaust port shape
· Rigid mount silencer
· Transmission ratios changed for 3rd and 4th gears
· Reduced clutch operational load
CHASSIS
The new aluminium Bilateral Beam frame has been engineered specifically to work with the 250cc engine. The engine and components such as the radiator and fuel tank have been distributed to centralise the bike’s mass, so that it turns-in effortlessly on tight corners. The new design features increase lateral and torsional rigidity, giving more feedback on the terrain. The increased rigidity also helps to redirect sideways shocks vertically, transferring the energy into the absorbent suspension.
Suspension
Improvements have been made to the damping valve and the inner rod of the YZ250F’s long-stroke front suspension to ensure a better feel when turning-in on fast corners, giving the rider more confidence to power through the bends. At the rear, the position of the spring of the suspension unit has been lowered 29 mm in order to enable a straight intake passage - resulting in better cushioning performance over bumps in the track
New dimensions
The bike’s caster and trail dimensions have also been optimised to make the most of the new engine and chassis configuration, further improving handling and performance.
ENGINE
Updated for 2010, the YZ250F’s liquid-cooled 4-stroke DOHC single-cylinder 5-valve engine features revised carburettor settings and improved ignition characteristics.
The result of all these modifications is more linear power delivery through the rev-range for better control at low to mid speed.
Aluminium retainer intake
The engine’s intake/exhaust valves now feature lightweight aluminium retainers and new valve springs which open more easily, minimising power loss and providing more torque at low speeds.
New carburettor settings and funnel shape
To accommodate the changes in the intake/exhaust systems the settings of the carburetor have been optimised. The spec of the cam for the acceleration pump and the shape of the air passage on the air-cleaner side contributing to improved power development at low to medium speeds. On the air cleaner itself, the funnel-shape has been optimised and the cleaner box modified to fit the new frame.
Exhaust port
The shape of the exhaust port has been optimised from a round cross-section to a “D” cross-section to contribute to the new engine character.
Rigid mount silencer
The size of the diffuser pipe in the silencer has been changed along with the size of the noise-reducing punched-hole pipe to achieve optimum performance. In keeping with the YZ250F’s use of lightweight parts, a lighter rigid silencer mount has been adopted.
Revised gear ratios
To aid mid-range performance the gear ratios for 3rd and 4th gears have been changed: 3rd gear has been changed from the 1.450:1 to 1.444:1, and 4th from 1.227:1 to 1.222:1
New design reduces clutch operational load
The clutch spring load has been changed. Also, the length of the push lever cam has been modified to change the lever ratio and reduce operational load.
New-design crankcase cover
The new-design crankcase cover has been designed with serviceability in mind. The new oil-level gauge window provides an at-a-glance view of the oil and the drain-bolt position has been changed for easier access.
Styling
The YZ250F’s greater poise and agility are reflected in the new-for-2010 styling. The new bodywork is much sleeker, and the surface area of exterior parts has been minimised creating a feeling of lightness and accentuating the bike’s compact, dart-like shape. The new textured plastic parts keep the bike looking its best - even after a hard ride on the track. A Competition White version is offered as a second colour in addition to the classic Yamaha Blue - both feature fashionable black wheel-rims.
Better riding
Rider ergonomics are better catered for with four-step adjustable handlebars and a new-design flat seat developed specifically for the YZ250F. The seat surface material offers the perfect combination of grip and ease of sliding – letting the rider shift their bodyweight easily to control the bike, but providing reassuring grip when needed. The surface texture is designed to resist clogging of the surface grain with sand or mud to ensure superior grip and reduce the amount of dirt build-up after a ride.
Lightweight parts
The leaner YZ250F features new lightweight parts throughout – including a new design sprocket, plastic resin engine protector, a more compact oil tank, optimised brake pedals and smaller brake hose guides. As part of the new styling package, lightweight exterior parts have been adopted including new slimmer shapes for the front fender, rear fender, front number plate, front fork protector, side covers and air scoop.
Accessories
The following accessories are available for the 2010 YZ250F:
· Aluminium skid plate
· Aluminium frame guards
· Aluminium radiator guards
· Sticker kit: protects the bike from scratches and gives it a whole new appearance. Matches with the optional new seat skin
· Seat skin: replaces the original seat skin, giving it a new look
