| Component | Specification |
|---|---|
| Production Years | 2015 – 2019 |
| Engine Oil | SAE 10W-40 API SG/JASO MA |
| Oil Capacity | 0.85L (Periodic), 0.90L (With Filter), 1.10L (Dry) |
| Tires (F/R) | 80/100-21 51M / 110/100-18 64M |
| Tire Pressure | 1.0 bar (15 psi) Front & Rear |
| Spark Plug | NGK LMAR8G |
| Battery | YTZ7S |
The Yamaha WR 250 F (CG42W/BAKD) represents a pivotal moment in enduro engineering. When launched in 2015, it was the first WR-F model to adopt the revolutionary rearward-slanted, reverse-cylinder head engine architecture. By placing the intake at the front and the exhaust at the rear, Yamaha achieved a level of mass centralization previously unseen in the 250cc enduro class, significantly reducing the bike’s rotational inertia and enhancing flickability through tight technical sections.
Engineering Evolution
Derived directly from the championship-winning YZ250F motocross platform, the CG42W iteration brought fuel injection and a 6-speed wide-ratio transmission to the woods. The cylinder head design allows for a straight intake tract, maximizing volumetric efficiency. For the WR-F variant, Yamaha engineers tuned the ECU and exhaust specifically for a broader powerband, ensuring tractable torque for steep climbs and technical obstacles.
Maintenance Essentials
Lubrication System
The high-revving nature of the 250cc DOHC engine demands strict adherence to lubrication intervals. Use only high-quality SAE 10W-40 API SG/JASO MA oils. For a standard periodic oil change without filter removal, 0.85L is required. If the filter is replaced (highly recommended every second oil change), the capacity increases to 0.90L. A total dry engine rebuild requires 1.10L.
Ignition & Electrical
The CG42W utilizes a high-efficiency NGK LMAR8G spark plug. Given the tight tolerances of the reverse-head design, ensure the plug is torqued correctly to prevent compression leaks. The electrical system is powered by a compact YTZ7S battery, which provides the necessary cold cranking amps for the electric start system even in cold weather conditions.
Chassis & Handling
Equipped with industry-leading KYB SSS (Speed Sensitive System) front forks, the WR 250 F offers unparalleled damping consistency. To maintain the intended handling characteristics, tire pressures should be maintained at 1.0 bar (15 psi) for both the 80/100-21 front and 110/100-18 rear tires. Lower pressures may be utilized for extreme muddy conditions, but risk rim damage in rocky terrain.
Expert Verdict
The 2015-2019 WR 250 F remains a benchmark for reliability and performance. While it requires more frequent maintenance than a dual-sport bike, the rewards are found in its professional-grade suspension and a chassis that feels significantly lighter than its physical weight suggests. It is the definitive choice for riders transitioning from amateur trails to competitive enduro racing.