| Specification | Data |
|---|---|
| Model Series | JA4B / JA48 |
| Engine Type | 125cc SOHC Air-Cooled Single |
| Oil Specification | SAE 10W-30 API SG+ (JASO MA) |
| Oil Capacity | 0.8 Liters |
| Tire Size (Front/Rear) | 70/90-17M/C 38P / 80/90-17M/C 50P |
| Tire Pressure (F/R) | 2.0 bar (29 psi) / 2.25 bar (33 psi) |
| Battery | YTZ7S |
| Spark Plug | NGK CPR6EA-9S |
The Honda Super Cub C125 (JA4B/JA48) represents a pivotal moment in the lineage of the world’s most produced motor vehicle. While it retains the classic step-through silhouette established in 1958, the JA4B series is historically significant for being the first Super Cub to transition from a utilitarian tool to a premium lifestyle machine, featuring a unique cast aluminum wheel design and a standard front-wheel ABS system—technologies previously reserved for Honda’s larger displacement motorcycles.
Engineering Analysis: The JA4B Powerplant
At the heart of the C125 is a 125cc air-cooled, four-stroke SOHC engine. Unlike its predecessors, this unit emphasizes refined power delivery and reduced NVH (Noise, Vibration, and Harshness). The engine utilizes a semi-automatic centrifugal clutch paired with a four-speed transmission, allowing for clutchless shifting that remains the hallmark of the Cub experience. The inclusion of Programmed Fuel Injection (PGM-FI) ensures Euro 4 compliance and exceptional fuel economy, often exceeding 60km/L in real-world conditions.
Maintenance & Service Guidelines
For the Editor-in-Chief’s recommended service intervals, adherence to the following technical parameters is critical for maintaining the C125’s longevity:
- Lubrication: Use only 0.8L of SAE 10W-30 oil meeting JASO MA standards. The centrifugal clutch shares the engine oil, so friction modifiers found in ‘Energy Conserving’ automotive oils must be avoided to prevent clutch slippage.
- Ignition System: The NGK CPR6EA-9S is the specific heat range required. Ensure the plug gap is set to 0.8–0.9 mm to maintain optimal combustion stability.
- Electrical: The YTZ7S battery supports the Smart Key system. If the bike is stored for more than two weeks, a trickle charger is recommended to prevent parasitic drain from the keyless entry module.
Handling and Safety
The JA4B features a rigid backbone steel frame optimized for the 125cc output. The 17-inch cast wheels provide significantly better lateral stability compared to traditional wire spokes. Safety is bolstered by a 220mm front disc brake equipped with a single-channel ABS, providing a necessary safety net for urban commuting on variable surfaces.
Frequently Asked Questions
What is the oil change interval for the C125?
Honda recommends an initial oil change at 1,000 km, followed by every 6,000 km. However, for urban stop-and-go riding, MotoSpecsLab recommends a 3,000 km interval.
Can I use 10W-40 oil?
While 10W-30 is the factory standard for optimal fuel efficiency and flow, 10W-40 JASO MA is acceptable in climates consistently exceeding 35°C (95°F).
What is the chain slack specification?
The drive chain slack should be maintained between 25–35 mm to prevent premature wear of the countershaft sprocket and rear hub bearings.