CG 125cc Cylinder Assy Pin 15mm

CG125 Aluminum Alloy Cylinder Assembly

Replacement Cylinder for CG125 Air Cooled Engine

Set includes: Aluminum cylinder block, piston, piston rings, piston pin

This product is a replacement cylinder assembly designed for the classic CG125 air-cooled engine. The cylinder block is manufactured from high-quality aluminum alloy with a cast iron liner, combining the excellent heat dissipation of aluminum with the wear resistance of a cast iron bore, ensuring stable engine operation and long service life. This assembly includes all the core components needed for an engine overhaul, making it an ideal choice for your repair or upgrade project.

We offer two versions of the CG125 cylinder assembly, distinguished by the piston pin diameter. CG125 engines have had different design specifications throughout their long production history. The most common version uses a 15mm piston pin, but some early or specific models use a 13mm pin.

Please take the following steps BEFORE purchasing:

• 1. Measure your original piston pin: Use a caliper to measure the diameter of your old piston pin.
• 2. Confirm the specification: Select the 13mm or 15mm version based on your measurement.
• 3. Note: Choosing the wrong version will result in the piston pin not matching your connecting rod small end, making installation impossible.

• Aluminum Cylinder + Cast Iron Liner: This composite construction offers the best of both worlds: lightweight and rapid heat dissipation from the aluminum, combined with the wear-resistant durability of a cast iron bore, significantly extending engine life.
• Precision-Matched Piston Components: The piston, rings, and pin are precision-matched to the cylinder, ensuring optimal clearances and sealing for stable compression right after installation.
• High-Quality Piston Rings: The rings offer excellent elasticity and wear resistance, effectively sealing the combustion chamber and controlling oil consumption.
• Direct Replacement: Manufactured to original CG125 specifications, all mounting dimensions (cylinder height, stud spacing, etc.) are identical to the original part, allowing for a direct bolt-on replacement with no modifications.

✅ Typical Symptoms Indicating Cylinder Replacement: Hard starting, significant loss of power, excessive oil consumption (blue smoke from exhaust), noticeably low compression, unusual engine noises (such as knocking). If you experience these issues and confirm the cylinder is worn beyond limits, it's time to replace this assembly.

⚠️ Installation Note: Thoroughly clean the crankcase mating surface before installation. When installing the piston, note the direction arrow on the piston crown (usually pointing towards the exhaust side). When installing the piston rings, stagger their end gaps (typically 120 degrees apart). Always use a new cylinder head gasket and tighten the cylinder head nuts to the specified torque and sequence according to your service manual. Proper engine break-in is essential after installation.