Even though Yamaha has had a winning range of dirt bike models for the last few years, featuring the rather unique reverse cylinder engine design on the 4-stroke models that enables such an effective mass-centralising design, it’s great to see they have still found ways to make several refinements on their 2017 models.
Some nice performance improvements can be expected from the YZ250F and YZ250FX which boast the most significant changes including a new cylinder head and intake system. The ECU mapping has been revised, along with the inlet and exhaust ports to increase power. Cam lift has been increased, the throttle body venturey shortened to increase mid and top power, and the Piston and gudgeon pin lightened and strengthened to increase power. A new stronger Conrod is fitted to cope with the additional power and for improved durability. The big end features new thrust washers which reduce friction. Even the crankcases have been strengthened thanks to a new heat treating process. The gearbox will also provide smoother and more reliable shifting due to refinements in design and machining.
Fuel level and engine warning lights have been added. The Exhaust header pipe diameter has also been changed to increase power.
Across the range new brake pad material and a new 270mm front brake rotor replaces the old 250mm unit to provide great stopping power and control for more aggressive cornering. Yamaha’s Kayaba suspension is already highly rated by most riders yet the new models feature further optimised suspension settings for better comfort and performance and new fork seals which self-clean better to improve durability.
All models now feature black rims and new graphics and all 4-stroke models come with an improved new airbox cover. The Big Blue’s YZ and WR models have steadily been increasing their market share in South Africa over the last few years and these changes are sure to see them building on that and doing even better.