| Component | Specification |
|---|---|
| Engine Oil | SAE 10W-40 (API SG+; JASO MA) – 1.00 L |
| Front Tire | 100/80-17 M/C 52H (2.00 bar / 29 psi) |
| Rear Tire | 130/70-17 M/C 62H (2.25 bar / 33 psi) |
| Spark Plug | NGK CR9E (Gap: 0.7–0.8 mm) |
| Battery | YTZ6V (12V Maintenance Free) |
A unique engineering highlight of the Yamaha MT-125 (RE114/RE115) is its shared DNA with the YZF-R125 supersport. Unlike many entry-level nakeds of its era that utilized budget commuter frames, the MT-125 was built around a high-rigidity steel Deltabox frame. This choice provided the 125cc class with a level of lateral stiffness and handling precision previously reserved for higher-displacement performance machines, effectively spearheading the ‘Dark Side of Japan’ ethos in the learner category.
Technical Deep Dive: Engine & Chassis
The RE11 series features a liquid-cooled, 4-stroke, SOHC, 4-valve single-cylinder engine. While the displacement is modest, the engineering is sophisticated. The forged aluminum piston and the offset cylinder design reduce friction and heat, allowing the engine to reach its peak power of 11.0 kW (15.0 PS) at 9,000 rpm reliably. The 41mm inverted (USD) front forks provide excellent feedback, distinguishing it from the conventional telescopic forks found on its competitors.
Maintenance Guide: Professional Service Standards
To maintain the MT-125’s high-revving performance, strict adherence to fluid specifications is mandatory. At MotoSpecsLab, we emphasize the use of JASO MA rated oils; using friction-modified automotive oils will lead to premature clutch slippage in this wet-clutch system.
Ignition and Electrical
The NGK CR9E spark plug is critical for the high-compression ratio of this engine. Ensure the gap is precisely set between 0.7 and 0.8 mm to prevent misfires at high RPM. The YTZ6V battery is a compact AGM unit; if the bike is stored during winter, a smart-charger is required as the ECU has a small parasitic draw for the immobilizer system.
Tires and Safety
The MT-125 utilizes a 100/80-17 front and a 130/70-17 rear setup. Maintaining the factory-specified 2.00 bar (Front) and 2.25 bar (Rear) is essential for the bike’s agility. Under-inflation significantly dulls the steering response, a common complaint among new riders neglecting weekly checks.
MotoSpecsLab Verdict
The RE114/RE115 generation of the MT-125 remains a benchmark for build quality in the 125cc segment. Its combination of a supersport-derived chassis and a reliable, high-tech engine makes it an ideal platform for both novice riders and urban commuters seeking premium performance. Proper maintenance of the cooling system and high-quality synthetic oil are the keys to longevity for this high-strung single.