| Component | Specification |
|---|---|
| Model Code | RJ42A / L2 |
| Production Years | 2010–2012 |
| Engine Oil | SAE 10W-40 API SF/SG or SH/SJ (JASO MA) |
| Oil Capacity | 0.9 L |
| Spark Plug | NGK R0452A-10 |
| Tires (Front) | 80/100-21 51M |
| Tires (Rear) | 100/90-19 57M |
| Tire Pressure | 1.0 bar (15 psi) F/R |
| Battery | None (Kick-start only) |
The 2010 introduction of the RJ42A marked a pivotal moment in motocross history: it was Suzuki’s first 250cc four-stroke to ditch the carburetor in favor of a sophisticated Electronic Fuel Injection (EFI) system. This engineering shift, derived directly from the RM-Z 450, eliminated the infamous ‘bog’ associated with hard landings and off-camber jumps, setting a new benchmark for throttle response in the MX2 class.
Engineering Overview
The RJ42A features a 249cc, DOHC, four-valve engine. The standout feature is the 43mm Keihin throttle body with a progressive linkage. Unlike many competitors of the era, Suzuki engineered the system to operate without a battery, utilizing a magneto-driven charging system and a capacitor to provide the initial surge required to power the fuel pump upon kicking the lever.
Maintenance & Technical Specifications
Lubrication System
For the RM-Z 250, oil quality is paramount due to the high-revving nature of the valvetrain. MotoSpecsLab recommends a high-grade 10W-40 JASO MA compliant oil. The capacity is a precise 0.9 liters. Given the lack of an external oil cooler, frequent changes (every 5-6 hours of track time) are critical to prevent thermal breakdown.
Ignition and Combustion
The RJ42A utilizes a specialized NGK R0452A-10 spark plug. This is a racing-spec component designed to withstand the high cylinder pressures and temperatures of a tuned EFI engine. Ensure the gap is checked regularly, as fouling can lead to difficult starting—a common complaint if the EFI mapping or air filter maintenance is neglected.
Chassis and Handling
The ‘L-series’ chassis is renowned for its ‘corner-at-all-costs’ geometry. To maintain this precision, tire pressures should be kept at 1.0 bar (15 psi) for both the 80/100-21 front and 100/90-19 rear. Deviating from these pressures significantly alters the footprint and can lead to front-end tucking in tight ruts.
Editor’s Verdict
The Suzuki RM-Z 250 RJ42A remains a favorite for riders who prioritize handling and immediate power delivery. While it requires disciplined maintenance—specifically regarding the fuel system filters and oil intervals—it offers one of the most communicative chassis ever produced in the 250cc class.