The YZ250F is aimed at taking the quarter litre motocross class to the next level. Design goals of the new machine are increased power and optimal handling. The reverse-engine layout that has proved so successful on the 450 was selected to achieve these goals.
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The engine features a fuel injection system, with revised fuel and ignition timing, that gives a great throttle response and doesn’t need to be set to temperature or altitude like a carb does.
The development team has made the new 250F smaller, lighter and easier to use. The reversed engine layout also helps with concentrating the heavy masses around the centre of gravity.
With its front facing inlet and rear exiting exhaust, the YZ250F's innovative reverse cylinder head offers many advantages over a conventional design. These include increased intake and exhaust efficiency, as well as enhanced mass centralisation thanks to the use of a top-mounted air filter and underseat fuel tank. Yamaha's engineers have taken this cutting-edge technology to the next level, and developed a new reverse cylinder head that gives the YZ250F rider even stronger mid to high rpm pulling power.
Using feedback from our factory teams, Yamaha has been able to fine-tune the frame in order to ensure that YZ250F riders are able to fully exploit the increased engine performance of the uprated model. Compared to the 2016 design, the 2017 frame is around 12mm wider in the area behind the swingarm pivot point, and this increased torsional rigidity ensures a higher degree of handling stability.
Increased rideability and comfort have been achieved on the 2017 YZ250F through a number of revisions to the front and rear suspension. The class-leading Air Oil Separate (AOS) KYB® front forks feature a new more rigid outer tube design and slightly reduced oil capacity, and these changes - together with new factory suspension settings – give improved rider feedback for improved chassis performance and stability in ruts, bumps and corners.
To achieve a roomier riding position that best suits a wide range of racers, the footrest position on the 2017 YZ250F has been lowered by 5mm. This also helps to lower the centre of gravity to give increased control in ruts and corners.
For improved brake feel, the 245mm rear disc is manufactured using the same heat resistant steel as the 270mm front disc, giving total braking confidence on the fastest tracks.
Quick release fastners on the airbox allows for easy access, to the large capacity air filter.
The muffler is moved forward. The exhaust pipe, which needs a certain length for good low and mid range torque, winds around the cylinder head like a snake, centralising weight.
|Engine Type||Liquid-cooled, 4-stroke, DOHC, 4-valves|
|Bore x Stroke||77 x 53.6 mm|
|Lubrication System||Wet sump|
|Fuel Management||Fuel Injection|
|Fuel Tank Capacity||7.5 L|
|Oil Capacity||0.9 L|
|Final Transmission||Constant mesh 5-speed|
|Seat Height||965 mm|
|Ground Clearance||330 mm|
|Dry Weight||99 kg|
|Wet Weight||105 kg with 7.5 litres of fuel|
|Frame Type||Bilateral Beam|
|Suspension Front||Telescopic fork, 310mm travel|
|Suspension Rear||Swingarm (link suspension), 315mm travel|
|Brakes Front||Hydraulic 270mm single disc|
|Brakes Rear||Hydraulic 245mm single disc|
|Tyres Front||80/100-21 MS32|
|Tyres Rear||100/90-19 MS32|