| Specification | Data |
|---|---|
| Model Year | 2015 |
| Model Code | CG23C / 1SS2 |
| Engine Type | 249cc Liquid-cooled 2-stroke; reed-valve inducted |
| Transmission Oil | 0.75 L (10W-40 JASO MA) |
| Spark Plug | NGK BR8EG |
| Front Tire | 80/100-21 51M (1.0 bar / 15 psi) |
| Rear Tire | 110/90-19 62M (1.0 bar / 15 psi) |
Engineering Highlight: The Aluminum Legacy
While most manufacturers abandoned the two-stroke platform in the mid-2000s, Yamaha executed a masterstroke by introducing the semi-double-cradle aluminum frame in 2005. The 2015 CG23C (1SS2) model represents a significant aesthetic and functional milestone in this lineage. It was the first year Yamaha introduced the modern, aggressive bodywork styling—including the fenders, number plates, and airbox—that bridged the visual gap between the legendary two-stroke and the modern YZ-F four-stroke family.
Technical Performance & Power Delivery
The heart of the 1SS2 is its 249cc liquid-cooled engine, renowned for its broad powerband and the Yamaha Power Valve System (YPVS). Unlike many high-strung race engines, the YZ 250 offers a unique torque curve that provides usable pull from the mid-range through the top end. This versatility is why the 2015 model remains a favorite for both motocross racing and technical off-road hare scrambles.
Maintenance Guide: Ensuring Peak Performance
Transmission Lubrication
The CG23C requires exactly 0.75 Liters of oil. For optimal clutch performance and gear protection, MotoSpecsLab recommends Yamalube 4 (10W-40) or a high-quality SAE 10W-40 that meets JASO MA standards. Using oil without the JASO MA rating can lead to premature clutch slippage due to friction modifiers.
Ignition and Combustion
The 2015 YZ 250 is tuned specifically for the NGK BR8EG spark plug. This fine-wire electrode plug is critical for preventing fouling during low-speed technical riding while maintaining heat dissipation during high-RPM wide-open throttle sections. Always verify the gap before installation to ensure consistent ignition timing.
Chassis and Contact Patch
The 1SS2 utilizes a 21-inch front and 19-inch rear wheel setup. For standard track conditions, we recommend a baseline pressure of 1.0 bar (15 psi) for both the 80/100-21 front and 110/90-19 rear tires. Adjusting by +/- 2 psi is acceptable depending on terrain density (lower for sand, higher for hard-pack rocks).
MotoSpecsLab Verdict
The 2015 Yamaha YZ 250 (CG23C/1SS2) is more than just a motorcycle; it is a testament to mechanical refinement. Its combination of the SSS (Speed Sensitive System) KYB suspension and a proven two-stroke powerplant makes it one of the most serviceable and rewarding machines in the history of motocross. Proper adherence to the 0.75L oil capacity and NGK plug specifications ensures this machine will remain competitive for decades.