| Specification | Value |
|---|---|
| Model Series | CJ25W / B7R9 |
| Production Years | 2019–2023 |
| Engine Oil | Yamalube 4 10W-40 (0.68 L) |
| Spark Plug | NGK LMAR8G |
| Battery | HJTZ5S-FP-VIC (Lithium-ion) |
| Tire Size (F/R) | 90/90-21 / 130/90-18 |
| Tire Pressure | 1.0 bar (15 psi) Front & Rear |
Engineering Highlight: The CJ25W generation of the WR 450 F represents a pivotal moment in enduro engineering, utilizing a unique “reversed” cylinder head design. By positioning the intake at the front and the exhaust at the rear, Yamaha achieved superior mass centralization and a straighter intake tract, directly translating to more linear torque and improved handling agility compared to traditional layouts.
Technical Review: Performance and Architecture
The 2019–2023 Yamaha WR 450 F is more than just a YZ450F with a headlight. The B7R9 variant features a frame specifically tuned for enduro flex characteristics, providing the rider with essential feedback over technical terrain. The engine management system is calibrated for a smoother power delivery, ensuring traction in low-grip scenarios while retaining the explosive top-end power the 450cc platform is known for.
Maintenance Guide: Fluids and Ignition
For peak performance, lubrication is critical. The WR 450 F operates with a relatively small oil volume of 0.68 Liters. MotoSpecsLab recommends using Yamalube 4 10W-40 meeting API SG and JASO MA standards. Due to the high-revving nature of the CJ25W engine, oil changes should be frequent, especially after heavy competitive use.
Ignition is handled by the NGK LMAR8G spark plug. Given the tight tolerances of the reversed cylinder head, ensuring the plug is correctly gapped and torqued is vital for consistent starting and throttle response.
Chassis and Electrical Systems
The transition to the HJTZ5S-FP-VIC lithium-ion battery in this generation significantly reduced weight and improved cold-start reliability. However, owners should use a lithium-specific charger to maintain the battery’s lifespan during off-season storage.
For the wheelset, the 21-inch front and 18-inch rear combination is optimized for off-road stability. Maintaining a pressure of 1.0 bar (15 psi) is the factory standard for mixed terrain, though competitive riders may adjust this based on specific track conditions and the use of rim locks.
Expert Verdict
The Yamaha WR 450 F (CJ25W/B7R9) remains a benchmark in the large-displacement enduro category. Its combination of motocross-derived power and enduro-specific chassis tuning makes it a formidable tool for both amateur trail riders and professional rally racers. Adhering to the strict maintenance schedule outlined above is essential for preserving the longevity of this high-performance machine.