| Component | Specification |
|---|---|
| Production Years | 1982 – 1999 |
| Engine Oil | SAE 10W-40 (1.5 L) |
| Front Tire | 3.00-18 47P |
| Rear Tire | 120/90-16 63P |
| Tire Pressure (F/R) | 1.75 bar (25 psi) / 2.00 bar (29 psi) |
| Battery Type | YB10L-A2 |
| Spark Plug | NGK DR8EA |
Did you know that the Suzuki GN 250 was the primary training vehicle for the Motorcycle Safety Foundation (MSF) in the United States for decades? Its inclusion wasn’t accidental; the NJ42A platform features Suzuki’s Twin Swirl Combustion Chamber (TSCC), a design intended to improve flame front velocity and combustion efficiency, making it one of the most reliable single-cylinder engines ever produced.
Technical Review: The NJ42A Legacy
The Suzuki GN 250 (NJ42A) is the quintessential ‘UJM’ (Universal Japanese Motorcycle) in cruiser clothing. Produced for nearly two decades, its longevity is a testament to its over-engineered air-cooled SOHC 4-valve engine. While it produces a modest 22 horsepower, the torque delivery is linear and forgiving, making it an ideal candidate for both urban commuting and lightweight touring.
From an engineering perspective, the NJ42A is remarkably accessible. The frame is a semi-double cradle design that provides stable handling at low speeds, though the 16-inch rear wheel choice leans more toward ’80s cruiser aesthetics than canyon-carving performance. The inclusion of a front disc brake was a significant upgrade during its early years, providing adequate stopping power for its 129kg dry weight.
Maintenance Guide & Essential Specs
Lubrication System
The GN 250 utilizes a wet-sump lubrication system. For optimal engine longevity, MotoSpecsLab recommends 1.5 liters of SAE 10W-40. Ensure the oil meets at least API SE or SG standards. Given the air-cooled nature of the NJ42A, frequent oil changes (every 3,000 – 5,000 km) are critical to prevent thermal breakdown.
Ignition & Electrical
The electrical system is powered by a YB10L-A2 battery. Cold cranking performance is essential as the GN 250 relies solely on an electric starter. The spark plug of choice is the NGK DR8EA; ensure the gap is set to 0.6–0.7mm for consistent ignition timing.
Chassis and Tires
The NJ42A uses a distinct wheel combination: an 18-inch front and a 16-inch rear. Maintaining the correct pressure is vital for handling: 1.75 bar (25 psi) in the front and 2.00 bar (29 psi) in the rear. Over-inflating the rear tire can lead to a ‘skittish’ feeling on uneven pavement due to the short wheelbase.
MotoSpecsLab Verdict
The Suzuki GN 250 – NJ42A remains a gold standard for mechanical simplicity. For the modern rider or enthusiast, it represents a ‘blank canvas’ for custom builds (Cafe Racers/Brats) or a bulletproof daily driver that requires only basic tools for a lifetime of service.