| Feature | Specification |
|---|---|
| Model Code | CG23C / 1SST (2015) |
| Engine Type | 249cc liquid-cooled 2-stroke; reed-valve inducted |
| Transmission Oil | Yamalube 4, SAE 10W-30 (0.75 L) |
| Spark Plug | NGK BR8EG |
| Tire Size (Front) | 80/100-21 51M |
| Tire Size (Rear) | 110/90-19 62M |
| Recommended Pressure | 1.0 bar (15 psi) F/R |
A hallmark of engineering longevity, the 2015 Yamaha YZ 250 (CG23C/1SST) represents a pivotal moment in the ‘Blue Crew’ history. While many manufacturers abandoned the two-stroke platform, Yamaha introduced a significant aesthetic and ergonomic refresh in 2015, featuring modern ‘Speed Block’ styling and the industry-standard KYB® Speed Sensitive System (SSS) fork—widely considered the finest production suspension ever fitted to a motocross machine.
Technical Engineering & Performance
The CG23C chassis utilizes a sophisticated semi-double-cradle aluminum frame, engineered to balance rigidity with the flex characteristics required for high-speed stability and cornering precision. The 1SST designation brought updated plastics and a new clutch lever reach adjuster, but the heart remains the legendary 249cc liquid-cooled power valve engine (YPVS), known for its broad, tractable powerband.
Maintenance Guide & Fluid Specifications
Engine Lubrication and Transmission
For the transmission, MotoSpecsLab recommends Yamalube 4, SAE 10W-30. The total capacity is 0.75 Liters. Regular changes every 3-5 hours of competitive use are essential to prevent clutch fade and ensure gear longevity. For the fuel mix, a high-quality 2-stroke synthetic oil at a 30:1 or 40:1 ratio is standard, depending on riding conditions.
Ignition System
The 2015 model utilizes the NGK BR8EG spark plug. It is critical to inspect the electrode color regularly; a ‘chocolate brown’ hue indicates optimal jetting. Ensure the gap is set to manufacturer specifications to prevent high-RPM misfires.
Tires and Traction Management
The YZ 250 comes equipped with a 21-inch front and 19-inch rear wheel setup.
- Front: 80/100-21 51M
- Rear: 110/90-19 62M
For standard track conditions, maintain a pressure of 1.0 bar (15 psi) in both tires to balance footprint and rim protection.
Editorial Review: The MotoSpecsLab Verdict
The 2015 Yamaha YZ 250 remains the gold standard for riders seeking a mechanical connection that modern four-strokes often mask. Its power-to-weight ratio is exceptional, and the maintenance simplicity of the CG23C platform makes it a favorite for privateer racers. The inclusion of the SSS suspension in this model year solidified its position as a ‘buy-and-race’ bike that requires very little aftermarket intervention to be competitive at the highest levels.