2019 Yamaha YZ250F Unveiled
Yamaha has released information about its all-new 2019 YZ250F. The bike is redesigned from the ground up and is now equipped with electric start and the first smartphone-engine tuning app to come as a stock feature on a production 250cc four-stroke motocross bike. All-new engine, frame, and bodywork are also major focal points of the completely new motorcycle.
For 2019, Yamaha has refined its distinct rearward-slanted cylinder design for the engine. Using a compact starter motor and lightweight lithium-ion battery, the 2019 YZ250F is now equipped with electric start, and the liquid-cooled, DOHC, four-valve, fuel-injected engine features a forward-positioned straight downdraft intake with symmetrical intake and exhaust ports. Fuel is delivered by a lighter 44mm throttle body through a new 12-hole Denso injector. A new, higher-compression flat-top forged piston has a bridge-box design for additional strength with minimal weight. The piston, rings, and DLC-coated piston pin, along with the offset cylinder configuration, are all designed to reduce friction loss and contribute to quick response.
The engine’s intake ports, cam profiles, connecting rod, and optimized crank and counterbalancer all work together to produce more potent mid-to-high-rpm power with user-friendly delivery and reliability. The new cylinder is also lighter and angled more upright to improve mass centralization. The transmission and clutch were also overhauled for a more direct connection as well as enhanced durability. The gears and shift drum have been revised for lighter weight, and the cogs and shift mechanisms are designed to smooth gear changes and improve durability under the heavy demands of motocross racing. A larger-diameter clutch is also a new feature, designed to improve feel and boost reliability even further under high-heat conditions. The valve cover of the engine is now blue on the Team Yamaha Blue bike as well.
The radiators and exhaust system have also been modified for improved performance and weight distribution. The updated radiators are larger and angled more directly into the incoming airstream for improved cooling under the most demanding race conditions. The wraparound exhaust pipe design improves mass concentration and power development, with revised geometry for 2019. The new layout moves the rear end of the exhaust pipe farther forward and enables a muffler position closer to the bike’s center of mass.
The 2019 YZ250F now has the capability to be tuned in different ways, including dual-mode switchable engine mapping, which can be done with the push of a button. Taking after what was first implemented on the YZ450F last year, the all-new YZ250F now features a wireless smartphone-based engine tuner that can be accessed by connecting to the bike’s onboard CAN-bus network via a Communication Control Unit (CCU) by Wi-Fi. Android and iOS users can download the Power Tuner app to adjust air-fuel mixture and ignition timing maps to tune engine performance for track conditions, record race log information, and monitor a range of data such as maintenance and system diagnosis, engine run time, and more. The valve cover of the engine is now blue on the Team Yamaha Blue bike as well.
The Yamaha YZ250F retains the Speed-Sensitive System (SSS) coil-spring-type fork found on the previous-generation machine but with updated settings, larger pistons, and newly designed fork lugs/axle brackets designed to provide a good balance between handling and bump absorption. The KYB shock has new damping characteristics to match the new chassis as well as a new, lighter-weight spring. Lastly, the shock reservoir has been increased by 30cc to increase damping control during long motos.
The aluminum bilateral beam frame is completely new for 2019, designed to improve contact to the ground and provide the best possible balance of stiffness for better bump absorption and cornering. The all-new frame features a redesigned swingarm pivot area along with redesigned upper frame bracing and rear frame spars. All-new engine mounts that centralize mass and increase rigidity on lateral, horizontal, and vertical axes provide an ideal balance between cornering feel and straight-line rigidity.
Surrounding the fully redesigned chassis, the YZ250F features a new lighter, compact body from tip to tail. The radiator shrouds incorporate a new air duct with a concave shape that not only improves styling but is also narrower for better knee grip and overall rider movement. The seat height has been reduced by 8mm (approximately 0.3 inch) toward the front and almost 20mm (approximately 0.8 inch) lower at the tail end, giving the rider better maneuverability on the bike. The cross-sectional profile of the bike’s blue Excel rims are lighter than the previous wheels, reducing unsprung weight without sacrificing durability, while wheel collars with increased rigidity are intended to provide an improved feeling of contact to the ground when braking and a clear feeling of traction.
The YZ250F is available in either Team Yamaha Blue or White color schemes, complete with the onboard Communication Control Unit (CCU) and the Yamaha Smartphone Power Tuner app, and will arrive at Yamaha dealers beginning this month for $8,199.