| Specification | Detail |
|---|---|
| Production Years | 1976 – 1979 |
| Engine Type | 247cc Air-cooled, 2-stroke, Parallel Twin |
| Transmission Oil | SAE 10W-30 / 20W-40 (1.3L Periodic / 1.5L Total) |
| Tires (F/R) | F: 3.00-18 / R: 3.25-18 |
| Spark Plug | NGK B8ES (Gap: 0.7 – 0.8 mm) |
| Battery | 12N5.5-3B |
The Yamaha RD 250 1A2 represents a pivotal moment in motorcycle history, marking the transition from the rounded, classic lines of the early 70s to the sharp, aggressive ‘coffin tank’ aesthetic that would define the late two-stroke era. While many enthusiasts focus on the later LC models, the 1A2 was the machine that perfected the air-cooled reed-valve ‘Torque Induction’ system, providing a power band that was surprisingly linear for a 250cc twin of its time.
Engineering & Performance Analysis
Underneath the 1A2’s angular bodywork lies an evolution of the 351/352 engine series. The 247cc parallel twin utilized Yamaha’s patented reed-valve induction, which significantly improved low-end response compared to traditional piston-port designs. The 1A2 designation also brought refinements to the frame and braking system, offering a more stable platform for the 30hp output.
Maintenance Guide: Keeping the Legend Alive
For the modern collector, maintaining the 1A2 requires precision, particularly regarding the lubrication and ignition systems. High-quality 2-stroke oil is non-negotiable for the Autolube system, but the gearbox requires specific attention.
Lubrication System
The gearbox requires SAE 10W-30 or 20W-40 oil. For a standard oil change (periodic), you will need 1.3 Liters. If the engine cases have been split for a total rebuild, the dry capacity is 1.5 Liters. Ensure the oil meets JASO MA standards to prevent clutch slippage.
Ignition & Electrical
The 1A2 relies on a 12V system powered by a 12N5.5-3B battery. For optimal combustion and to prevent fouling—a common issue in vintage 2-strokes—use NGK B8ES plugs. The gap must be precisely set between 0.7 and 0.8 mm to ensure consistent firing under high compression.
Chassis & Tires
The 1A2 handles best when tire pressures are strictly maintained. The standard fitment is 3.00-18 at the front and 3.25-18 at the rear.
- Front: 1.8 bar (26 psi)
- Rear (Solo): 2.0 bar (28 psi)
- Rear (Dual): 2.3 bar (33 psi)
Editor’s Verdict
The Yamaha RD 250 1A2 is more than a vintage motorcycle; it is a masterclass in 2-stroke engineering. Its reliability, provided the maintenance schedule is followed, remains impressive even by modern standards. For those seeking the raw, mechanical connection of a pre-liquid-cooled Yamaha, the 1A2 is the definitive choice.