| Attribute | Specification |
|---|---|
| Production Years | 2013–2018 |
| Engine Type | 249cc, 4-stroke, liquid-cooled, DOHC |
| Engine Oil | SAE 10W-40 API SG/SH/SJ/SL/SM JASO MA (0.9 L) |
| Spark Plug | NGK R0452A-10 |
| Front Tire | 80/100-21 51M (1.0 bar / 15 psi) |
| Rear Tire | 100/90-19 57M (1.0 bar / 15 psi) |
| Model Code | RJ42A / L5 Series |
The Suzuki RM-Z 250, specifically the RJ42A generation encompassing the L5 model, stands as a landmark in motocross engineering. A unique historical highlight of this platform is its pioneering use of the Showa SFF-Air (Separate Function Front Fork) system, which eliminated heavy coil springs in favor of three air chambers, significantly reducing unsprung weight and allowing for unprecedented levels of track-side tunability.
Technical Engineering Overview
At the heart of the RJ42A is a high-revving 249cc fuel-injected engine. During the 2013-2018 production run, Suzuki engineers focused on mid-range torque and throttle response. The implementation of the Keihin fuel injection system with a 44mm throttle body ensured precise atomization, which is critical for the high-compression (13.5:1) nature of this race-bred machine.
Maintenance Specifications
For the professional technician or the dedicated privateer, adhering to the following specifications is non-negotiable for engine longevity:
- Lubrication: The engine requires 0.9 liters of high-quality synthetic oil meeting JASO MA standards. Given the high-revving nature of the RJ42A, oil changes should occur every 5-8 hours of track time.
- Ignition: The NGK R0452A-10 is a specialized racing plug. Ensure the gap is checked and the plug is replaced if any fouling or electrode erosion is detected.
- Tire Pressure: For optimal traction and rim protection, a baseline of 1.0 bar (15 psi) is recommended for both the 21-inch front and 19-inch rear tires, adjustable based on track density.
MotoSpecsLab Editorial Review
The RM-Z 250 (RJ42A) remains one of the best-handling bikes in its class. Its ability to hold an inside line is legendary. While it may lack the electric start found on modern rivals, its mechanical simplicity and the reliability of the RJ42A platform make it a favorite for racers who prioritize chassis feedback and cornering precision over electronic gadgets.
Frequently Asked Questions
How often should I change the oil?
Under racing conditions, change the 0.9L of 10W-40 oil every 5 hours. For casual trail riding, 10 hours is the maximum limit.
Does the L5 model have a battery?
No, the RJ42A/L5 series utilizes a kickstart mechanism and does not feature an onboard battery for the ignition system.
What is the benefit of the NGK R0452A-10 plug?
This specific plug is designed to withstand the extreme heat and vibration of a high-performance 250cc motocross engine, preventing pre-detonation.