| Attribute | Specification |
|---|---|
| Model Series | CJ21C / B112 |
| Production Years | 2014 – 2017 |
| Engine Oil | Yamalube 4 (10W-40) API SG/JASO MA |
| Oil Quantity | 0.73 Liters |
| Front Tire | 80/100-21 51M |
| Rear Tire | 110/90-19 62M |
| Tire Pressure (F/R) | 1.0 bar (15 psi) / 1.0 bar (15 psi) |
| Spark Plug | NGK LMAR8G |
| Battery | Not Applicable (Kickstart only) |
The 2014-2017 Yamaha YZ 450 F (CJ21C) stands as a landmark in motocross engineering due to its revolutionary rearward-slanted cylinder design. While the concept debuted in 2010, the CJ21C generation perfected the ‘snaking’ exhaust and front-mounted intake system, which allowed for a near-perfect center of gravity and reduced the gyroscopic effect of the engine’s internal rotating mass.
Technical Performance & Handling
The CJ21C chassis was a significant departure from its predecessor, featuring a refined bilateral beam frame that provided better flex characteristics for cornering. The 449cc liquid-cooled DOHC engine utilized a 4-valve head (instead of the older 5-valve Genesis design), focusing on massive low-to-mid range torque. The B112 variant specifically benefited from updated ECU mapping and suspension valving that addressed the ‘twitchiness’ often associated with 450cc race bikes.
Maintenance Guidelines
To maintain the high-performance standards of the YZ 450 F, strict adherence to the service schedule is mandatory. The engine is a high-revving unit with tight tolerances.
- Lubrication: Use 0.73 liters of Yamalube 4 (10W-40). Because the oil capacity is relatively low for a 450cc engine, frequent changes (every 3-5 hours of racing) are critical to prevent thermal breakdown.
- Ignition: The NGK LMAR8G spark plug is specifically designed for the high-compression combustion chamber of this model. Ensure the gap is checked before installation.
- Tires and Traction: Standard sizing is 80/100-21 for the front and 110/90-19 for the rear. For optimal track performance, a pressure of 1.0 bar (15 psi) is recommended for both ends, though this may be adjusted slightly based on terrain density.
Professional Verdict
At MotoSpecsLab, we rate the CJ21C/B112 generation of the YZ 450 F as one of the most durable and ‘tunable’ platforms for intermediate and professional riders. The introduction of the GYTR Power Tuner compatibility during these years allowed riders to adjust fuel and ignition maps without a laptop, making it a pioneer in user-accessible EFI tuning.