Yamaha 2010 YZ250F

Yamaha announced the 2010 YZ250F today and it reflects a number of surprises, both for what it has and doesn’t have. The biggest change in direction is the frame. Yamaha abandoned the aluminum backbone design that it adopted in 2006 and switched to perimeter layout. It now resembles Honda, Kawasaki and Suzuki frame.
      Throughout the bike, there are dozens of other changes, including the suspension and bodywork. But the bike did not get EFI for 2010, with Yamaha evidently feeling that the market would not tolerate the increase in price. Here’s the run down:
* Airbox: The box is larger and the intake boot leading to the carb is straighter for better airflow.
* Carburetor: The venturi shape is smoother and the jetting is richer.
* Cam: Intake lift is altered from 7.6mm to 7.7mm. The valve stem end has a harder surface treatment.
* Valve train: Valve spring retainers are changed from steel to aluminum for less spring load.
* Head: Exhaust port shape is changed and has a flat bottom.
* Pipe: Mid pipe steps up from 45.0mm to 50.8mm.
* Silencer: Core size reduced from 42.7mm to 41.3mm. Within the core, the perforations are more widely spaced (from 4mm to 5mm). The goal is less noise.
* Clutch: Yamaha increased the spring load and then gave the actuation cam more leverage, with the end result an easier lever pull. The bushing at the center of the basket is said to be harder.
* Gearbox: Third, fourth and fifth gears are said to be stronger. The ratios of fourth and fifth are taller.
* Ignition: Mapping is altered.
* Frame: All-new twin-beam frame is made of forged sections and extruded sections; no castings. Lateral and torsional rigidity is increased.
* Steering head: Head tube is lower and more rearward for more compact rider compartment.
* Head stay: The frame-to-head mount was moved and another was added to work with new frame rigidity.
* Oil tank: The outboard oil tank is reshaped and reduced in capacity to fit in the new frame.
* Radiators: The location was moved 15mm down and 10mm back. An additional mount was added.
*  Steering head bearing: Top seal made 0.3mm thicker to prevent corrosion.
* Fork: New damping specifications are used along with new surface treatment for the piston rod. The seals have a new shape.
* Shock: New damping specs are used and the spring is now located 30mm lower on the body.
* Rider positioning: The YZ250F has a flatter seat, taller bars, higher footpegs and four-way adjustable bar mounts.
* Fuel tank: Reduced capacity.
* Body work: New plastic and styling; new plastic skid plate incorporates water pump guard.

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