| Component | Specification |
|---|---|
| Production Years | 2015 – 2018 |
| Engine Oil | SAE 10W-40, API SG+, JASO MA |
| Oil Capacity | 0.71L (Change) / 0.73L (Filter) |
| Tires (F/R) | 80/100-21 / 110/100-18 |
| Tire Pressure | 1.00 bar (15 psi) Front & Rear |
| Spark Plug | NGK LMAR8G (Gap: 0.7–0.8 mm) |
| Battery | YTZ7S |
The 2015 release of the Yamaha WR 250 F (CG42W/BAKJ) marked a paradigm shift in enduro engineering. It was the first model in the WR-F lineage to adopt the revolutionary rearward-slanted cylinder and forward-mounted fuel injection system, a technology directly inherited from the championship-winning YZ250F motocrosser. This design optimizes mass centralization, significantly improving the flickability and handling of the machine in tight technical terrain.
Technical Engineering Overview
The CG42W chassis is built around a bilateral beam aluminum frame, providing the necessary rigidity for high-speed stability while maintaining the flex characteristics required for enduro endurance. The heart of the machine is the liquid-cooled, 4-valve DOHC engine. Unlike its predecessors, the reversed cylinder head allows for a straight intake tract, maximizing volumetric efficiency and throttle response.
Maintenance Guide & Fluid Specifications
To maintain peak performance and engine longevity, following the strict lubrication and ignition parameters is critical for this high-revving power plant.
1. Lubrication System
The WR 250 F utilizes a sophisticated lubrication circuit. For standard maintenance, use a high-quality SAE 10W-40 oil meeting JASO MA standards to ensure wet-clutch compatibility.
- Periodic Change: 0.71 Liters
- With Filter Replacement: 0.73 Liters
- Total Dry Capacity: 0.85 Liters
2. Ignition and Electrical
The engine relies on a precise spark to manage its high compression ratio. The specified plug is the NGK LMAR8G. It is imperative to verify the electrode gap is between 0.7–0.8 mm before installation. For the electrical system, the lightweight YTZ7S battery provides the necessary cold cranking amps while keeping the overall weight low.
3. Chassis and Tires
For optimal traction on varied terrain, the CG42W utilizes a 21-inch front and 18-inch rear wheel setup.
- Front Tire: 80/100-21 51M
- Rear Tire: 110/100-18 64M
- Standard Pressure: 1.00 bar (15 psi) for both front and rear. Adjustments may be made based on terrain (lower for mud/sand, slightly higher for rocky terrain to prevent pinch flats).
MotoSpecsLab Verdict
The Yamaha WR 250 F (2015-2018) remains a benchmark for 250cc four-stroke enduros. Its transition to the YZ-based engine platform transformed it from a reliable trail bike into a competitive racing weapon. For owners, the key to reliability lies in frequent oil changes and air filter maintenance, as the high-performance top end is sensitive to contaminants.