Finally, the construction contributes

Finally, the construction contributes

In hardly any other type of motor sport are the material requirements in terms of reliability. Performance as extreme as in motocross. And just here the Yamaha YZ250F set standards again and again not only in technical regard. Since its brand launch in 2001 and debut in the 2003 FIM World Championship, the YZ250F has marked the benchmark in four-stroke technology. In 2003, none other than motocross legend Stefan Everts even managed the feat of winning all three championship rounds held on one day – in other words, all classes – and in the following five years, the four-stroke Yamaha helped seven riders to notable successes – including two world championship titles for the fabulous Antonio Cairoli. To this day, the YZ250F has remained the sports bike for winners. This is demonstrated by such talented young riders as Zach Osborne and Loic Larrieu in the MX2 World Championship; or Christophe Charlier, who is currently dominating competition in the MX2 European Championship. Also in the 2010 model year Yamaha relies on the incomparable racing genes. Sends the four-stroke to the track with once again optimized performance. This means that the best-equipped YZ250F remains the first choice for young riders who want to be at the front of the pack on the race track.

Curve potential as the key to faster lap times

Yamaha's race development engineers know exactly why motocross races are won or lost in the corners. Pilots also favor a machine that allows them to turn into corners faster and accelerate out sooner. And that's why the YZ250F was designed from the start for maximum cornering potential. A well controllable engine performance designed. Of course, these talents do not mature overnight, but require integrated, coordinated development of the engine, frame, suspension and other components.

Technical highlights

Chassis and styling

  • Newly designed aluminum bridge frame
  • Modified steering head angle and caster
  • Telegabel optimized in detail
  • Suspension strut with modified suspension spring position
  • Newly designed flat bench
  • Newly designed fuel tank
  • New lightweight components
  • New styling with slimmer attachments
  • Second color variant in Competition White (not in all markets)

Engine

  • Optimized engine characteristics
  • Aluminum valve cone pieces and lightweight valve springs
  • New carburetor tuning and intake manifold
  • Modified exhaust port
  • Stiffer muffler mounting
  • Modified gear ratios for the 3. And 4. Gear
  • Reduced clutch actuation forces

CHASSIS

The new aluminum bridge frame was specially designed for the 250cc four-stroke engine. Engineers positioned the single cylinder and other components such as the radiator and fuel tank to maximize mass centralization. This makes the engine particularly easy to direct into tight bends. The new frame layout also features increased lateral and torsional stiffness for improved off-road feedback. Finally, the design helps to deflect lateral forces vertically so that they can be better absorbed by the spring/damper elements.

Spring/damper elements

Engineers have also fine-tuned the long-travel telescopic fork. Improvements to the damper valve and piston rod give more feel in fast corners and increase the rider's confidence in his machine. At the rear, the suspension strut has a 29-millimeter lower suspension spring. This solution ensures straighter guidance during compression and improves shock absorption on bumps and moguls.

Changed chassis geometry

Steering head angle and caster were also modified. Modified chassis geometry allows engine and frame to interact optimally and improves handling qualities and performance potential.

ENGINE

For the 2010 model year, the liquid-cooled DOHC single-cylinder, four-stroke, five-valve engine features modified carburetor tuning and optimized ignition.

As a result, the engine delivers smoother power delivery across the rev range and is easier to control, especially at low and medium speeds.

Aluminum valve cone pieces

In the new model year, the intake and exhaust valves feature lightweight aluminum valve cone pieces. Also new valve springs with lower spring stiffness facilitate the opening process and ensure lower power losses and higher torque output at low engine speeds.

New carburetor tuning, reshaped intake manifold

Carburetor tuning has been adapted to the intake and exhaust changes. A revised cam for the accelerator pump and modified air passage in the carburetor favor power development at low and medium engine speeds. The air filter box itself has also been revised. Shape adapted to the new frame. In addition, the airbox has an optimized intake funnel.

Exhaust port

To reflect the changed engine characteristics, the round exhaust port has been replaced by an optimized D-shaped cross-section.

Stiffer muffler mounting

For reasons of performance optimization, the engineers modified the entire pipe system in the muffler. Finally, the rigid muffler mount – like many other components on the new YZ250F – is lighter in weight.

Modified gear ratios

The modified gear ratio in 3. And 4. Gear benefits the power potential in the medium engine speed range. In the 3. Gear, the transmission ratio is now 1.444:1 instead of 1.450:1, in the 4. Gear 1.222:1 instead of 1.227:1.

Reduced actuation forces for the clutch

The modified clutch spring force and the modified length of the release lever result in lower manual forces when operating the clutch.

New molded crankcase cover

When redesigning the crankcase cover, engineers had the engine's serviceability in mind. The new oil sight glass allows inspection at a glance, while the oil drain plug is now even more accessible.

Styling

The confident and dynamic appearance of the YZ250F in the 2010 model year is due not least to the overall slimmer styling. The surfaces of many add-on parts are now more minimalist. Thus creating the impression of lightness. At the same time, they emphasize the machine's compact, arrow-shaped design. Finally, the new textured plastic parts ensure a flawless appearance at all times – even after a hard run on the track. In addition to the classic color scheme in Yamaha Blue, a second color scheme in Competition White is now also available. Both versions are equipped with black rims.

Optimized ergonomics and drivability

Pilots of different statures benefit from four-way adjustable handlebars and a new flat seat designed specifically for the YZ250F. Its covering material offers a perfect combination of slip resistance and smoothness: On the one hand, the driver can shift his weight effortlessly in order to control his machine, on the other hand, he finds enough grip and adhesion, if this is required. In addition, the surface structure is particularly dirt-repellent. Sand or mud can hardly settle, so that the balanced properties of the new cover are maintained even in hard use.

Lightweight components

The significantly slimmed-down YZ250F is equipped with many new, particularly lightweight components. These include a modified pinion, plastic engine guard, more compact oil tank, optimized foot brake lever and narrower guides for the brake lines. In line with the new styling, many plastic parts are also significantly slimmer and lighter. Examples are the front and rear fenders, the front number holder, the fork protectors, the side fairing and the air scoop.

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