Yamaha Releases all-new YZ250F for 2010

First out of the gate for "official" 2010 news is Yamaha Motor Corp, with their all new - reworked YZ250F, featuring a sky-high 13,500 rpm redline. Details and hi- res photos below...

2010 YZ250F

The new YZ250F... designed specifically for 250 class competition


* For 2010 the YZ engineers have focused on optimizing the intake & exhaust systems, lightened the valve train, revised the carburetor settings and improved the ignition advance characteristics. These improvements result in improved low to mid power and a more rider friendly engine with a more linear power delivery for improved drivability and control.
* New, liquid-cooled, 250cc, DOHC, 5-titanium valve, 4-stroke engine features a 13,500-rpm redline.
* Short skirt forged piston reduces weight and vibration, plus offers excellent durability.
* The 13.5:1 compression ratio provides fast, controlled combustion and excellent engine performance.
* Optimized 5-valve (3-intake & 2-exhaust) combustion chamber design provides the most efficient intake and exhaust flow for maximum power.
* Titanium valves decrease weight by more than 40% over a conventional steel valve train and reduce reciprocating mass for faster-revving.
* All new aluminium valve retainers reduce inertial mass for faster throttle response
* New "load reduced" valve springs reduce the amount of force required to open the valves and thereby minimizes power losses associated with friction and improves torque in the low and mid ranges.
* Special chromium nitride coating on the tips of the intake valve stems reduces wear.
* Exhaust port shape has been revised from a round to a "D" shape to optimize flow and improve performance and engine character
* Revised intake cam profile further improves performance.
* The lightweight "liner less" aluminium cylinder features a ceramic composite coating which insures faster, more uniform heat dissipation, reduced friction and a longer service life.
* Cylinder design features cutaways that allow the air trapped under the piston to enter a side chamber (or cutaway) to reduce horsepower-robbing "pumping losses."
* Revised lightweight engine crankcase also utilizes special cutaways to reduce "pumping losses." The crankcase cutaways match the cutaways in the cylinder for maximum efficiency.
* Relocated convenient oil sight glass window and oil drain plug.
* Lightweight magnesium cylinder head cover.
* Dry sump lubrication system uses a remote oil tank reservoir positioned in front of the engine. This revised oil tank is lighter and more compact for 2010 and features a partition in the centre of the tank that improves the air-oil separation function. This tank is positioned low in the chassis which centralizes mass and lowers the centre of gravity for exceptional handling and a light feeling.
* Oil volume in the engine has been optimized to reduce weight and "oil drag" related power losses.
* Revised, 5-speed transmission features "involute splines" on the transmission axles to ensure smooth shifting and instant hook-up under power. The gear ratios for 3rd and 4th gears and the engagement dog shape have been changed to maximize the engine improvements. 3rd gear ratio = 26/18(1.444) while 4th gear ratio is 22/18(1.222).
* Lightweight engine counterbalancer reduces vibration for improved rider comfort and less rider fatigue.
* Revised multi-plate wet clutch features a revised clutch boss insert for improved wear, clutch spring load has been increased and the length of the push lever cam has been revised to change the lever ratio for an easier clutch lever pull and improved clutch feeling.
* Lightweight, "quick-access" outer clutch cover provides fast, easy access for clutch maintenance.
* Compact design automatic cam chain tensioner reduces maintenance and mechanical engine noise
* Revised Keihin FCR-MX37 flat-slide carburetor with throttle position sensor (TPS). The carb settings have been revised to accentuate the improvements in the intake and exhaust systems. The cam for the accelerator pump has been optimized while the shape of the carburetor "throat" on the air box side has been modified for improved air flow.
* The air box assembly has been revised for improved performance. The funnel shape at the air box "outlet" is optimized, while an all new straight design "boot" between the air box and the carb also improves air flow.
* Washable, dual-stage, foam air filter.
* No fuss auto decompression system means fast, easy starting. The YZ250F restarts in any gear.
* Convenient, handlebar-mounted hot start lever ensures fast starts when the engine is hot.
* Revised CD ignition system delivers a precise spark and monitors engine rpm to insure optimal timing for fast, strong response at all rpms. The ignition timing advance curve has been revised for improved performance.
* Direct ignition system means the ignition coil is integrated into spark plug cap to reduce weight and complexity.
* New compact, lightweight, single core, dual radiators provide outstanding cooling efficiency. The location of the rads has been lowered and moved rearward for improved performance and protection while also lowering the all important center of gravity and centralizing mass. The thickness of the cores has also been increased. For 2010, the revised rads mount to the new frame at 3 points.
* Lightweight titanium exhaust header pipe reduces weight, improves performance and allows hassle-free replacement of the oil filter.
* The lightweight exhaust system utilizes a 4-stage expansion format that improves the cylinder filling induced by the exhaust pulse effect, resulting in excellent power characteristics.
* Revised rigid mount muffler assembly is 50mm longer than last year for improved performance and reduced noise levels. The size of the internal diffuser pipe and the noise reducing "punched hole pipe" have been modified to achieve optimum performance.
* The muffler can be repacked to maintain peak performance and reduced noise. The lightweight aluminium / stainless steel muffler complies with current CMRC & AMA noise regulations for 2010.
* Trick, oversized "barrel adjuster" on the clutch lever perch allows on-the-fly clutch adjustments.


* All new, compact "bilateral beam" aluminium frame centralizes mass for exceptional handling and cornering ability. This 250cc class specifically designed frame consists of forged, extruded and panel aluminium parts. This all new frame is more compact than the last generation and offers significantly improved "rider - machine communication" (a.k.a. feedback). The key goal of this new chassis is faster and easier cornering … one of the keys to winning races. The engineers started with a clean sheet of paper and designed the chassis based on the requirements of a 250cc motocrosser. Note: the YZ250F frame is unique unto itself.
* The rigidity balance of this new frame has been optimized and features increased lateral and torsional rigidity compared to the last generation frame. It also contributes to a feeling of lightness, agility and traction.
* The head pipe (steering head), wheelbase, caster and trail dimensions are optimized to accentuate the new engine and frame character. The benefit is incredible turning ability and quick, stable handling.
* New removable rear sub frame is constructed of square-section, lightweight aluminium pipe. Its detachable design allows easy access when servicing rear suspension components.
* Lightweight, tapered, aluminium swingarm is produced using "hydro forming", a special method that uses high pressure water to form shapes. The swingarm design provides great overall chassis "balance" for precise cornering and a light handling feel.
* Forged aluminium upper triple and lower triple clamps reduces weight and improve strength.
* Pro Taper handlebars are one of the most sought after style of bars. The Pro Taper bars provide excellent strength and durability. Foam handlebar pad is included.
* Handlebar position has been raised 5mm for 2010 to suit the new, more compact frame. The revised handlebar holders (with the upper triple clamp), offer a total of 4 different positions, and an adjustment range of 30mm, to better suit a wide variety of riders.
* Revised 48mm, adjustable, inverted, Kayaba cartridge fork features a twin-chamber design. The twin chamber design means the damper unit is in a separate structure which prevents aerated fork oil from entering the inner damper assembly and degrading its damping abilities. Since the inner damper is pressurized, it also prevents air bubbles forming in the oil. Front fork adjustments include: 20-way compression damping and 20-way rebound damping. Optional fork springs are available through Genuine Yamaha parts.
* Fork damping settings have been revised for 2010. The shape of the outer fork tubes, the inner piston rod design, and the low friction fork oil seals are also revised. The engineers focused on the enhancing the ground holding capabilities of the front wheel, a key for precise cornering.
* The 48mm inverted KYB fork also features a Transfer Control Valve (TCV) system. The TCV enhances the damping force of the inner damper from mid stroke to full stroke and improves bottoming characteristics. The benefit of TCV is more precise control throughout the full stroke. The TCV is located on the upside of the spring and its function is controlled by piston speed, not piston position … hence the term "Speed Sensitive fork".
* Front wheel travel is 300mm or 11.8"
* Revised, large "wrap-around" plastic fork protectors provide excellent lower fork tube protection. The "self-supporting" design reduces friction for smoother fork operation.
* Revised Monocross link rear suspension system features a fully adjustable Kayaba, piggyback shock which features separate adjusters for high- and low-speed compression damping. Adjustments include: spring preload, 20-way rebound damping, 20-way low-speed compression damping and 2 turns of high speed compression damping.
* The shock spring location has been lowered 29mm to accommodate the new intake boot.
* The shock uses an 18mm diameter piston rod. Kashima coating is used in the shock body and sub tank to reduce friction and improve suspension performance during a long moto. The Kayaba shock utilizes a full rebound oil lock system for excellent suspension function and great ride quality.
* Rear wheel travel is 307mm (12.1").
* 250mm floating front wave-style disc reduces weight and is squeezed by a Nissin twin piston caliper.
* 245mm rear disc brake features a lightweight "wave-style" disc and a single piston Nissin caliper.
* Compact and lightweight rear master cylinder is an integrated design (fluid reservoir is integrated into the top of the master cylinder) for strong stopping power with excellent feel and control.
* Newly designed rear pedal tucks in tighter to the engine / frame and reduces weight.
* Newly designed, compact body work includes front number plate, front fender, rad shrouds, fuel tank, side panels and rear fender which enhance the lightweight feel and look of the new YZ250F. This new "minimal " bodywork is a flat design, allowing fast, easy rider movements. The ergonomics provide a natural and roomy riding position. The body has been designed to maintain it good looks throughout the life of the machine.
* The lightweight, plastic resin 6.4 litre fuel tank compliments the chassis and has been moved closer to the rider for centralization of fuel tank mass and compactness.
* Redesigned seat is unique to the 250F. The surface texture has been designed to give a grip when needed, yet still allow easy rider movements. The "gripper" style seat cover has been designed to resists clogging with dirt or mud to ensure long lasting good looks.
* New lightweight Sun Star rear sprocket.
* Lightweight, 21" front and 19" rear Excel rims provide exceptional durability and help reduce unsprung weight for optimal suspension performance and handling.
* Rear wheel assembly uses a large 25mm diameter axle and a rear hub design which features a second bearing on the sprocket side for increased rigidity and durability.
* Bridgestone knobby tires offer competition-spec traction and excellent wear. Front = M403 / rear = M404.


* All new rugged polypropylene engine and integrated water pump protector plate reduces weight.
* "Shorty" adjustable front brake lever. Adjustment range is 5.5mm.
* New heavy duty plastic rear caliper and lower rear disc protectors.
* Large fuel cap and filler hole ensures easy opening and fast, hassle-free refuelling.
* New lightweight, extra wide foot pegs are 5mm lower and provide excellent grip and improved rider comfort.
* Lightweight header pipe heat shield.
* Serrated rear brake pedal for extra grip
* Folding gear shifter tip
* Stainless steel inner clutch cable provides excellent strength and durability.
* Lightweight chain guide / support helps reduce chance of chain derailment. It also helps protect rear sprocket from damage too.
* Heavy duty rubber swingarm protector
* Heavy duty DID 520 drive chain

Source: Bikeland.org

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