New Blues
By TMX Archives on 21st Aug 13
THE 2014 Yamaha YZ250F is the most exciting new MXer of the season, because it is exactly that new!Theres an all-new chassis housing an all-new engine and certainly for a 250F its a pretty radical package.
At the heart of the beast is an all-new reverse-head motor with the cylinder inclined rearwards, exactly like its bigger sibling the YZ450F.
The 450 has been around for several seasons now and Yamaha has held off releasing its first efi 250 four-popper until the launch of the eagerly awaited 2014 model.
The reverse head is perfect for efi as it allows a virtually straight intake tract and airbox at the front of the motor.
The fuel tank then sits in a much more central position to boost the centre of mass.
The challenge of this layout, with rear-facing exhaust ports, is obtaining enough length in the pipe for optimum performance.
Drawing on their experience with the 450, which itself has been revised for 2014, Yamaha has a unique front pipe that snakes 360 degrees right round the cylinder.
An all-new aluminium twin-spar chassis houses the motor.
Yamaha points out that this is not a simple construction but comprises 10 different types of forged, cast and extruded sections to guarantee exactly the right strength and flexibility to give optimum handling and performance.
The ergonomics are improved with a very slim profile, while detail like the front-wheel spindle diameter being increased from 20 to 22mm, improves rigidity and helps keep the front wheel bang on line.
The air-box is easily accessible, the transmission has been refined for slick shifting, the bars are rubber-mounted and the fuel tank capacity has been increased to 7.5litres.
And the graphics are now ‘in-mould' for greater durability.
