| Specification | Value |
|---|---|
| Production Years | 2007 – 2010 |
| Engine Type | Single-cylinder, Liquid-cooled, 4-stroke |
| Fuel System | PGM-FI (Programmed Fuel Injection) |
| Engine Oil | SAE 10W-30 API SG; JASO T 903 MA (0.8 L) |
| Spark Plug | NGK CR8E |
| Battery Type | YTZ7S |
A pivotal engineering highlight of the Honda CBR 125 R (JC39) was its transition from the carburetor system of its predecessor (the JC34) to Honda’s proprietary PGM-FI (Programmed Fuel Injection). This upgrade was not merely for Euro 3 emissions compliance; it fundamentally transformed the bike’s throttle response and cold-start reliability, cementing its status as the gold standard for entry-level sportbikes in the late 2000s.
Technical Performance & Engineering
The JC39 features a 124.7cc liquid-cooled SOHC engine. While the power output remained near the 10 kW (13.6 hp) mark to satisfy licensing restrictions, the fuel injection system allowed for a more linear torque curve. The chassis remains a lightweight pentagonal steel twin-spar frame, providing the flickable handling characteristic of the CBR series. Its narrow profile and 17-inch wheels make it an exceptional tool for urban commuting and learning technical cornering skills.
Maintenance Guide & Essential Specs
To maintain the longevity of the JC39, adhering to strict fluid and component specifications is vital. The engine is notoriously robust but sensitive to oil quality.
Lubrication System
The Honda CBR 125 R JC39 requires 0.8 liters of engine oil. We recommend SAE 10W-30 API SG that meets JASO T 903 MA standards to ensure the wet clutch operates without slipping. Regular changes every 4,000 km (2,500 miles) are advised for optimal performance.
Tires and Traction
The JC39 utilizes a specific narrow-profile tire setup to maintain its agile handling:
- Front: 80/90-17 M/C 44P (Pressure: 2.00 bar / 29 psi)
- Rear: 100/80-17 M/C 52P (Pressure: 2.00 bar / 29 psi solo; 2.25 bar / 33 psi with passenger)
Electrical & Ignition
The ignition system relies on a high-performance NGK CR8E spark plug. For the electrical system, the bike uses a YTZ7S battery. Given the fuel-injected nature of the JC39, maintaining a healthy battery is crucial, as the PGM-FI system requires stable voltage to operate the fuel pump and ECU during startup.
MotoSpecsLab Verdict
The Honda CBR 125 R JC39 remains a masterclass in small-displacement engineering. Its transition to fuel injection made it a significantly more mature motorcycle than the original 2004 model. For owners, the JC39 offers a rare combination of high-revving fun and remarkably low maintenance costs, provided the basic service intervals are respected.