| Attribute | Specification |
|---|---|
| Model Series | CJ25W / B7R4 |
| Production Years | 2021 – 2023 |
| Engine Oil | Yamalube 4 (10W-40) JASO MA / API SG (0.95 L) |
| Tire Dimensions | F: 80/100-21 51M / R: 120/90-18 65M |
| Operating Pressure | F: 1.0 bar (15 psi) / R: 1.0 bar (15 psi) |
| Battery Type | Skyrich HJTZ5S-FP-C (BR9-82100-01) |
| Spark Plug | NGK LMAR8G |
A unique engineering hallmark of the CJ25W generation is the industry-leading ‘reversed’ cylinder head layout. While Yamaha pioneered this in 2010, the 2021–2023 B7R4 iteration refined the architecture with a significantly more compact cylinder head and revised intake/exhaust port geometry. This design places the intake at the front and the exhaust at the rear, allowing for a straight downdraft intake tract that maximizes volumetric efficiency while centralizing mass for unparalleled handling agility.
Technical Engineering Overview
The CJ25W chassis represents a significant evolution in Yamaha’s bilateral beam frame technology. Derived from the YZ450F motocrosser but tuned with specific flex characteristics for enduro competition, the frame provides the necessary feedback for high-speed desert sections and technical single-track. The integration of the 449cc liquid-cooled engine with the Power Tuner app compatibility allows riders to adjust fuel and ignition mapping via smartphone—a feature that remains the gold standard in the segment.
Maintenance Protocol & Fluids
To maintain the high-performance tolerances of the B7R4 engine, strict adherence to fluid specifications is mandatory. The lubrication system requires 0.95 Liters of Yamalube 4 (10W-40) meeting JASO MA and API SG standards. Given the high-revving nature of the 450cc powerplant, oil shear is a concern; frequent intervals are recommended under race conditions.
Ignition is handled by the NGK LMAR8G spark plug. This long-reach plug is critical for the deep-combustion chamber design of the reversed head. For the electrical system, Yamaha utilizes a lightweight Lithium-Ion Skyrich HJTZ5S-FP-C battery, which is essential for maintaining the bike’s low center of gravity and ensuring reliable cold-starts in remote locations.
Wheel and Suspension Setup
The WR 450 F utilizes a dedicated enduro wheelset featuring an 18-inch rear rim to accommodate larger tire sidewalls for better traction over rocks and roots. The standard tire fitment is an 80/100-21 51M front and a 120/90-18 65M rear. For optimal performance across varied terrain, a baseline pressure of 1.0 bar (15 psi) is recommended for both front and rear, though this may be adjusted downward for extreme mud or upward for high-speed rally stages.
Expert Verdict
The Yamaha WR 450 F (CJ25W) remains the definitive choice for riders seeking a ‘competition-ready’ machine with Japanese reliability. Its unique engine configuration and advanced electronics suite make it one of the most versatile large-bore enduro bikes ever produced. Regular maintenance of the air filter and strict adherence to the 0.95L oil capacity will ensure this high-performance machine delivers years of peak service.