Yamaha YZ250F video and pics

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The 2010 YZ250F appears in this full gallery and video to give you a look at the new bike. The chassis has been completely redesigned, now featuring a bilateral beam frame and new riding position. The aim has been to get the rider further to the front of the bike, for better cornering and overall handling.

There have been a few engine changes too, including a new valve train, carburettor and exhaust all making for a more powerful and lighter bike. Check out all the images and specs below, with some of the main features highlighted.

Yamaha YZ250F 2010

Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010

Yamaha YZ250F 2010

Ask any motocross rider where races are won and lost and odds on he’ll tell you its all in the corners. A light, nimble and supreme handling MX bike can pick its lines and stick to them,
enabling its rider to hang on longer and go harder. So it’s no surprise to learn that cornering performance was the guiding theme throughout the development of the new model YZ250F.

The next generation motocross development plan was hatched with rider involvement paramount. Trackside customer research led Yamaha engineers to discover that what riders wanted more than anything else was sharp handling. Riders of all abilities from pros right down to swappers. And by handling, they meant better cornering performance. Because a better handling bike lets a rider get on the gas sooner, is less tiring to ride and is the key to winning motocross races.

Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010

The development team’s goal was to make quick cornering easy for riders of all skill levels. Not a simple task and certainly not something that could be achieved with small tweaks to the chassis or engine. The goal could only be reached by applying a highly innovative and synergistic approach to the science of motorcycle cornering.

The engineers were well aware that the 250 is not just a smaller displacement version of the 450, but a unique machine in its own right. So the task was to design a stand alone 250, not a scaled down 450cc MX bike.

By making a specific 250cc machine, the chassis can be tailored to deliver the handling response suitable for the class. The engine character of the 250 can then be tuned to suit that chassis. And by starting from a clean sheet of paper, not only was the goal of enhanced cornering performance met, the machine’s overall performance was dramatically improved.

The new YZ250F is compact, lightweight and requires little input for rider balance. Which means it’s less tiring to ride. The credit for this goes to the all new Bilateral Beam aluminium frame which features high lateral and torsional rigidity and offers a stable feel and precise handling.

Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010

The new frame converts sideways shocks smoothly to longitudinal shocks that are more readily absorbable by suspension. This makes the YZ250F very stable when cornering, which means it’s easier to dive into corners with more speed. By quantifying rider feedback, the chassis’ rigidity could be more precisely matched to the rider. Additionally, the new frame layout made it possible to change the shape of the fuel tank. By moving the tank towards the centre of the bike, mass centralisation was significantly advanced. Further improvements were made by moving the radiator rearward and mounting it lower.

Improvement to the initial damping quality of the front and rear suspension units have resulted in improved traction and give the rider a better feel for the terrain. This allows more confidence when entering a turn and lets the rider hold a line with less effort. The result is less rider fatigue during a long moto.

After thorough research and testing, Yamaha engineers decided to retain Yamaha’s five titanium valve engine layout and FCR carburettor fuel delivery system. This combination was found to produce the best power output for the displacement while maintaining compact engine dimensions and light weight. But the engine has been thoroughly refined for 2010 to result in even more punch. A higher lift intake camshaft, revised exhaust port and carb intake Flat and angular styling not only looks fast, it offers easy rider movement. Ergos are spacious and suit a wide range of riders.

Lightweight valve train means less inertial mass which minimises power loss and results in improved low to mid range power delivery funnel shapes, new valve springs and retainers, smaller oil tank and revised ignition map for the CDI are just some of the many detail improvements that have been made to the 250cc powerplant. The new frame also allowed a reshaping of the air cleaner box which improves intake efficiency. The result is a more rider friendly engine with more linear power delivery. Low- and mid-range power
characteristics and response are improved, giving the bike a lighter feel when cornering.

The changes were made possible in part by a measurement device used in MotoGP. This device allowed the engineers to quantify the transitional power characteristics when the rider begins to open the throttle after corner entry (1/4 – 1/2 throttle opening). Based on this data the engineers tuned the engine’s response characteristics to give the engine an ideal power feeling for the rider. Another small but important change was to modify the clutch lever ratio so as to reduce the effort required at the lever. This makes it much easier for the rider to slip the clutch.

The YZ250F’s straight frame-work directly expresses the lightweight feel and look a 250 should have. The plastic parts have been made as small as possible while still retaining their protective functions. The bike’s lightness is further expressed by emphasising its linear imagery. The flatness of the tank, seat and rear fender also facilitates rider movement and the relationship between the handlebars, pegs and seat make for a natural and roomy riding position. The dart-like styling allows function to follow form, as the YZ250F’s elegant design contributes to its winning potential.

Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010 Yamaha YZ250F 2010

2010 YZ250F key dimension change chart

Change made 2009 model 2010 model:
Silencer outer pipe tube length 380mm now 325mm
Silencer tail pipe length 40mm shorter than 2009
Radiator fixation points 2 now 3
Cylinder head fixing point number 1 point to 2 points
Intake cam lift 7.6mm now 7.7mm
Exhaust cam shaft flange diameter 27mm now 29mm
Intake valve spring wire diameter 2.2mm now 2.1mm
Exhaust valve spring wire diameter 2.5mm now 2.4mm
Exhaust pipe joint with silencer diffuser pipe diameter 50.8mm now 45.0mm / 50.8mm
Clutch spring screw washer number changed from 2 to 1
Clutch push lever cam height 4.4mm 2010: 4.0mm
Frame head pipe position 12 mm lower than 2009
Caster angle 27.1 degrees now 27.4 degrees
Trail 117.4mm now 119.6mm
Wheelbase 1476mm now 1473mm
Ground clearance 371mm now 376mm
Handle holder height 39mm now 44mm
Number of aluminium parts in frame About 20
Rear suspension 29 mm lower than 2009
Wet weight 102.8kg now 102.0kg

Overall length 2166mm
Overall width 825mm
Overall height 1304mm
Seat height 990mm
Wheelbase 1473mm
Minimum ground clearance 376mm
Wet (with oil and a full fuel tank) 102.0kg
Engine type
Liquid cooled 4-stroke,DOHC,5- valve
Cylinder arrangement Forward-inclined single cylinder
Displacement 250cm3
Bore & stroke 77.0 X 53.6mm
Compression ratio 13.5 : 1
Starting system type Kick starter
Lubrication system Dry sump
Radiator capacity (including all 1.0 litres routes)
Engine oil capacity 1.2 litres
Air filter type Wet element
Fuel tank capacity 6.4 litres
Carburettor Type/Fuel supply FCR-MX37 X 1
Ignition system type C.D.I
Spark plug model CR8E
Primary reduction system Gear
Primary reduction ratio 57/17 3.353
Secondary reduction system Chain
Secondary reduction ratio 51/13 3.923
Clutch type Wet, multiple-disc
Gear ratio
Transmission type Constant mesh 5-speed
Operation Left foot operation
Gear ratio-1st gear 30/14 2.143
Gear ratio-2nd gear 28/16 1.750
Gear ratio-3rd gear 26/18 1.444
Gear ratio-4th gear 22/18 1.222
Gear ratio-5th gear 25/24 1.042
Frame type Bilateral Beam
Caster angle 27.4°
Trail 119.6mm
Tyre size (Front) 80/100-21 51M
Tyre type (Front) Bridgestone M403A
Tyre size (Rear) 100/90-19 57M
Tyre type (Rear) Bridgestone M404
Brake type (Front) Hydraulic single disc brake
Brake type (Rear) Hydraulic single disc brake
Diameter of disc (front/rear) 250mm/245mm
Inside diameter of drum / Effective radius of disc (Front) 224mm
Inside diameter of drum / Effective radius of disc (Rear) 219.8mm
Suspension type (Front) Telescopic fork
Suspension type (Rear) Swingarm (link,suspension)
Shock absorber assembly type (Front) Coil spring/oil damper
Shock absorber assembly type (Rear) Coil spring/gas-oil damper
Wheel travel (Front) 300mm
Wheel travel (Rear) 310mm

Please note there are some small but significant differences between the Australian model and US model. And because AUS and Europe have different tyres, there are some differences to dimensions (eg length, seat height and ground clearance).

Key differences are:

- Silver rims on blue model, black rims on white
- Pointed muffler end cap
- Gearing 49/13
- Rear wheel travel 307mm
- Carb jetting
- Front suspension spring rate 4.4N/mm
- Bridgestone M403/M404 tryes

- Black rims on both colour models
- Rounded muffler end cap
- Gearing 51/13
- Rear wheel travel 310mm
- Carb jetting (same as AUS spec)
- Front suspension spring rate 4.5N/mm
- Pirelli Mid-Soft 32 tyres

- Black rims on both colour models
- Rounded muffler end cap
- Gearing 51/13
- Rear wheel travel 310mm
- Carb jetting (same as EUR spec)
- Front suspension spring rate 4.5N/mm
- Bridgestone M403/M404 tryes

Yamaha YZ250F 2010

Source | MCNews and Total Motorcycle

Video | Motocross Transworld

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