| Specification | Data |
|---|---|
| Production Years | 1977 – 1983 |
| Engine Oil | SAE 10W-40 (API SE/SF) |
| Oil Capacity | 0.8 L (Change) / 0.9 L (Total) |
| Tire Size | Front & Rear: 5.40 – 10 4PR |
| Battery | 6N4-2A-4 (6 Volt) |
| Spark Plug | NGK CR6HSA / C6HB (0.6 – 0.7 mm gap) |
The Honda CY 50, affectionately known in some markets as the “Naughty Dax,” represents a significant engineering pivot for Honda’s leisure bike lineup in the late 1970s. Unlike its predecessor, the ST50 Dax, which utilized a horizontal engine, the CY 50 was engineered with a sophisticated upright 49cc OHC engine derived from the CB50 and XL50 series. This design choice allowed for a more robust frame geometry and distinctive “balloon” tires, making it an early pioneer of the urban scrambler aesthetic.
Technical Engineering Overview
At the heart of the CY 50 is an air-cooled, four-stroke single-cylinder engine. The transition to an upright cylinder orientation improved cooling efficiency and allowed for a larger airbox configuration. The 5-speed transmission (on many European variants) offered a broader power band compared to the 3-speed semi-automatics common in the Monkey and Dax models of the era.
Maintenance Essentials
To maintain MotoSpecsLab’s standard of longevity, owners must adhere to the following technical parameters:
- Lubrication: Use a high-quality mineral-based 10W-40 oil. Modern synthetics may cause clutch slippage in these older wet-clutch systems. Ensure the oil meets API SE or SF standards.
- Ignition: The spark plug gap is critical for the 6V ignition system. Set the gap strictly between 0.6 mm and 0.7 mm using a feeler gauge.
- Chassis & Tires: The 5.40-10 tires are iconic but sensitive to pressure. Running them too low (under 1.0 bar) can lead to sluggish handling and sidewall cracking.
Electrical System
The CY 50 utilizes a 6-volt electrical system powered by a 6N4-2A-4 lead-acid battery. Given the age of these machines, ensure all grounding points are free of corrosion, as 6V systems are notoriously sensitive to voltage drops caused by poor connections.
Frequently Asked Questions
How much oil does the Honda CY 50 hold?
A standard oil change requires 0.8 liters. If the engine has been completely disassembled, the total capacity is 0.9 liters.
What is the recommended tire pressure?
Front: 1.0 bar (14.5 psi). Rear: 1.2 bar (17.4 psi) for solo riders, increasing to 1.5 bar (22 psi) when carrying a passenger.
Which spark plug is compatible?
The factory recommends NGK CR6HSA or C6HB. Always verify the gap is set to 0.6 – 0.7 mm before installation.
Editor’s Note: The Honda CY 50 remains a highly collectible piece of Honda’s small-displacement history. Proper maintenance of its unique upright engine ensures it remains as reliable today as it was in 1977.