| Parameter | Specification |
|---|---|
| Engine Type | 249cc, 4-stroke, Liquid-cooled, DOHC |
| Engine Oil | SAE 10W-40 (0.80 L) |
| Spark Plug | NGK CPR8EB-9 (Gap: 0.8–0.9 mm) |
| Tire Size (F/R) | 80/100-21 51M / 100/90-19 57M |
| Tire Pressure | 1.0 bar (14.5 psi) Front & Rear |
| Starting System | Kick-start (Capacitor-based ignition) |
The Torque Revolution: A Historical Engineering Perspective
The 2018 Kawasaki KX 250 F (model code KX252AAA/AJF) represents a significant milestone in Kawasaki’s development of the ‘quarter-liter’ class. While many manufacturers were chasing peak horsepower at the rev limit, Kawasaki engineers focused on a ‘torque-first’ philosophy for this iteration. A unique historical highlight of the 2018 model was the introduction of a revised intake path and a higher-pressure fuel pump (increased from 294 kPa to 343 kPa), specifically designed to improve low-to-mid range response. This made the KX 250 F one of the most accessible yet competitive machines for both intermediate racers and professionals alike.
Technical Engine Analysis
At the heart of the KX252AAA is the dual-injector fuel injection system. One injector is positioned downstream of the throttle valve for smooth response, while the second upstream injector delivers a high-volume mist at high RPMs. This setup requires precise maintenance of the electrical system. Note that this model is kick-start only; it utilizes a large-capacity capacitor to power the FI system during the kick, eliminating the weight of a lead-acid battery.
Maintenance Essentials
Lubrication System
For optimal performance of the high-revving DOHC valvetrain, MotoSpecsLab recommends using a high-quality synthetic SAE 10W-40 oil. The capacity is a lean 0.80 liters. Given the small oil volume and the high thermal stress of motocross racing, oil changes should be performed every 3-5 hours of competitive use to prevent viscosity breakdown.
Ignition & Combustion
The 2018 model utilizes the NGK CPR8EB-9 spark plug. Ensuring the correct gap of 0.8–0.9 mm is critical for reliable starting, especially since the bike relies on kick-starting. A fouled plug or incorrect gap can significantly increase starting effort on a hot engine.
Chassis & Handling
The KX 250 F features a slim aluminum perimeter frame designed for agility. To maintain the intended geometry and traction, tire pressures must be monitored closely. The factory recommendation is 1.0 bar (14.5 psi) for both the 21-inch front and 19-inch rear tires. Adjustments may be made based on track conditions (e.g., lower for sand, slightly higher for hard-pack), but 14.5 psi remains the engineering baseline for rim protection and carcass flex.
MotoSpecsLab Verdict
The 2018 Kawasaki KX 250 F remains a powerhouse in the used market. Its mechanical simplicity (lack of electric start) is offset by its sophisticated dual-injection system and robust mid-range power. For the technician, it is a straightforward machine to maintain, provided the strict oil change intervals and spark plug specifications are followed.