Engine
- Valve spring retainers are now lightweight aluminum instead of steel, and valve spring pressure is lighter for reduced valve opening force. This contributes to superior low-to-mid range torque characteristics due to less power-robbing friction. There's also a new, higher lift cam profile, while valve stem ends are chromium-nitride coated for exceptional reliability and reduced maintenance.
- The exhaust port shape has a "D" shape instead of round. This increases velocity through the port for excellent throttle response, while enhancing the power feeling of the engine.
- The newly designed radiator is lower and further back and the oil tank is more compact and repositioned to achieve greater mass centralization.
- The carburetor bore has a new venturi shape, plus there's recalibrated jetting and a new accelerator pump. This translates to impressive response when the rider snaps open the throttle, and contributes to superb torquey low-to-midrange power characteristics.
- The intake boot offers a straight, smooth tract for excellent engine breathing and more power. The airbox is reshaped to tuck neatly into the Bilateral Beam frame.
- The exhaust pipe has been carefully tuned to optimize engine power, with a muffler that's 50mm longer and with a narrower 57.7 incore – a design that lets the YZ250F comfortably meet the latest noise standards without sacrificing power.
- Engineers were able to increase the clutch spring load for stronger engagement, yet, thanks to a recalibrated clutch actuation arm cam ratio, lever pull is actually lighter than before.
Chassis/Suspension:
- The Bilateral Beam frame is crafted from a carefully chosen combination of forged and extruded aluminum pieces – 20 in all – all welded together to provide unmatched rigidity balance.
- The KYB® speed-sensitive front fork delivers exceptional damping feel, responsiveness, and bump absorption characteristics. Damping settings are revised, the piston rods have a new surface treatment, and the oil seal is a new design.
- The 4-way-adjustable KYB® rear shock has been redesigned to make the most of the Bilateral Beam frame design. It's lower in the frame for excellent mass centralization, and has new damping characteristics.
- The new tank, seat, and rear fender are flat and the relationship between handlebars, pegs, and seat result in a natural, more forward riding position that facilitates rider movement. The fuel tank has been moved toward the center of the bike for mass centralization. The ProTaper® bars are four-way adjustable, and handlebar mounts and footpegs are 5mm higher to optimize rider position on the new chassis.
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