| Specification | Value |
|---|---|
| Production Years | 2021 – 2023 |
| Engine Oil | SAE 10W-40, JASO MA (0.95 L) |
| Front Tire | 90/90-21 54M (1.0 bar / 15 psi) |
| Rear Tire | 130/90-18 69M (1.0 bar / 15 psi) |
| Spark Plug | NGK LMAR8G |
| Battery | HJTZ5S-FP-Z (Lithium-Ion) |
The Yamaha WR 450 F, specifically the CJ35W/BNK4 generation, stands as a testament to Yamaha’s ‘mass centralization’ philosophy. A unique engineering highlight of this model is its reversed cylinder head design. By placing the intake at the front and the exhaust at the rear, Yamaha achieved a straight downdraft intake tract, significantly increasing volumetric efficiency while positioning the heaviest engine components closer to the bike’s center of gravity for unparalleled flickability in tight woods.
Engineering Analysis & Performance
Sharing its DNA with the championship-winning YZ450F, the WR-variant features specific enduro tuning. The CJ35W utilizes a refined aluminum bilateral beam frame with tuned flex characteristics to absorb the impacts of technical terrain. The engine management system is optimized for a broader, more tractable powerband compared to its motocross sibling, ensuring the 450cc powerplant remains controllable on slippery climbs.
Maintenance Guidelines
To maintain the high-performance standards of the WR 450 F, strict adherence to the service schedule is mandatory. The 450cc liquid-cooled engine is a high-strung unit that demands quality lubrication.
Lubrication System
The system requires 0.95 Liters of SAE 10W-40 oil. It is critical to use oil meeting the JASO MA standard to ensure the wet multi-plate clutch operates without slippage. Given the high-revving nature of the BNK4 engine, MotoSpecsLab recommends oil changes every 10-15 hours of competitive use.
Ignition and Electrical
The CJ35W utilizes an NGK LMAR8G spark plug. Due to the compact cylinder head design, ensuring the plug is torqued correctly is vital for heat dissipation. The electrical system is powered by a lightweight HJTZ5S-FP-Z Lithium-Ion battery; always use a LiFePO4-compatible charger to avoid damaging the internal cells.
Chassis and Tires
For optimal traction, the standard fitment includes a 21-inch front and 18-inch rear wheel. For general enduro conditions, a pressure of 1.0 bar (15 psi) is the factory baseline. In extremely rocky terrain, increasing to 1.2 bar may prevent pinch flats, while soft mud may allow for 0.8 bar if rim locks are properly secured.
Final Verdict
The Yamaha WR 450 F CJ35W/BNK4 remains the gold standard for riders seeking a ‘ready-to-race’ platform that balances raw power with Japanese reliability. Its sophisticated chassis and reversed-engine layout offer a technical advantage that few competitors can match in the 450cc enduro class.