| Quick Specs: Yamaha RD 50 DX (353) | |
|---|---|
| Production Years | 1974 – 1979 |
| Engine Oil | SAE 10W-30 JASO MA (0.6 L) |
| Spark Plug | NGK B8HS (0.6 mm gap) |
| Tire Size (F/R) | 2.50 – 17 / 2.75 – 17 |
| Battery | 6N4-2A-4 (6V) |
While many 50cc machines of the 1970s were designed as simple utility mopeds, the Yamaha RD 50 DX (Type 353) was engineered with the soul of a Grand Prix racer. It was one of the first small-capacity motorcycles to feature Yamaha’s revolutionary “Torque Induction” system—a reed-valve intake design that allowed the two-stroke engine to deliver a wider powerband and superior low-end torque compared to its piston-port competitors.
Engineering Excellence: The 353 Legacy
The RD 50 DX was the premium evolution of the RD series, distinguished by its hydraulic front disc brake—a rarity for the 50cc class in 1974. The “DX” moniker signified its deluxe status, offering riders a scaled-down version of the legendary RD 350 experience. Its double-cradle frame provided handling characteristics that far exceeded the requirements of its 5-horsepower output, making it a favorite for young enthusiasts seeking a genuine motorcycle feel.
Maintenance Protocol
To maintain the high-revving nature of the 353 engine, strict adherence to technical specifications is required. The gearbox utilizes 0.6 Liters of SAE 10W-30 oil. For modern preservation, ensure the oil meets JASO MA standards to prevent clutch slippage.
Ignition and Electrical
The electrical system operates on a 6V architecture powered by a 6N4-2A-4 battery. Ignition health is paramount; the NGK B8HS spark plug must be gapped precisely to 0.6 mm. A fouled plug or incorrect gap on these small two-strokes will result in immediate starting difficulties and poor throttle response.
Chassis and Safety
Handling precision is dependent on tire condition and pressure. The RD 50 DX utilizes a 2.50 – 17 front tire and a slightly wider 2.75 – 17 rear. For optimal contact patch and rim protection, maintain pressures at 1.8 bar (26 psi) for the front and 2.0 bar (29 psi) for the rear.
Editorial Verdict
The Yamaha RD 50 DX – 353 remains a pinnacle of 1970s engineering. It represents a period where Yamaha refused to compromise on components regardless of displacement. For collectors, it is a mechanically rewarding machine that requires precise tuning but offers an unmatched vintage riding experience.
Frequently Asked Questions
Q: What is the fuel-to-oil mix ratio?
A: While the RD 50 DX featured the Autolube system, many owners choose to run a 50:1 pre-mix for added safety on vintage pumps.
Q: Can I use 10W-40 oil?
A: While 10W-40 is common, the original factory spec is 10W-30. If using 10W-40, ensure it is JASO MA rated for wet clutches.