2021 Yamaha YZ250F

Innovative and Upgraded Engine 
The liquid-cooled, DOHC 4-valve, fuel-injected engine features a forward-positioned straight downdraft intake with symmetrical intake and exhaust ports. For 2021, the engine has been updated with a new cylinder head featuring a new air intake system, an improved intake port shape, new exhaust camshaft profile, and an updated ECU—all to produce stronger mid- to top-end power and increased peak power, while retaining its class-leading low-end torque.

Exclusive Power Tuner App 
The free of charge and industry-exclusive Yamaha Power Tuner app brings the power of the GYTR Power Tuner to your iOS® or Android® device. Using wireless connectivity to talk to the bike’s onboard CAN-bus network, the app allows owners 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.

Adjustable Engine Maps 
Two-mode adjustable engine mapping allows the rider to adjust engine character with the push of a button, making it easy to tune the YZ250F for changing track or weather conditions.

Electric Starter System 
The YZ250F features a compact electric starter system that minimizes restart delays on track and adds convenience everywhere else. Powered by a high-capacity and ultra-lightweight, four-cell lithium-ion battery, the system adds minimal weight.

Piston, Rod and Crankshaft Balance 
A flat-top forged piston features a bridge-box design for additional strength with minimal weight. The piston, rings and DLC-coated piston pin, along with the offset cylinder configuration, all reduce friction loss and contribute to quick response. The engine’s intake ports, cam profiles, high-strength connecting rod and optimized crank and counterbalancer all work together to produce potent high-rpm power with user-friendly delivery and exceptional reliability.

Advanced Fuel Injection 
The adjustable fuel injection system uses a 44 mm throttle body, fed by a high-pressure electric fuel pump that injects fuel through a 12-hole Denso® injector. This ensures optimum fuel atomization and air/fuel calibration for excellent rideability in a wide range of riding conditions.

Wraparound Rear-Positioned Exhaust Layout 
An innovative exhaust pipe design improves mass centralization and power development characteristics. This layout moves the rear end of the exhaust pipe farther forward and positions the muffler closer to the bike’s center of mass.

Durable Transmission 
The transmission gears, dogs and shift mechanisms are designed to smooth gear changes and improve durability under the heavy demands of motocross racing. The YZ250F also features a large-diameter clutch to boost reliability even further under high-heat conditions.