Yamaha YZ125 58mm 144cc Athena Big Bore Kit – Top End Rebuild (1997–2004)

🛠️ Description
Upgrade your Yamaha YZ125 into a 144cc powerhouse with the Athena Big Bore Kit. This race-proven package includes everything you need for a full top-end rebuild, engineered for more horsepower, stronger torque, and factory-level reliability. Designed with precision machining and premium materials, it’s the ultimate bolt-on performance kit for riders who want to take their YZ125 to the next level.

✅ What’s Included

• Athena 58mm Nikasil Big Bore Cylinder (144cc)

• Athena Coated Piston Kit (Piston, Rings, Wrist Pin, Circlips)

• Athena Complete Top End Gasket Set

• Athena Cylinder Head w/ Bronze Dome Insert

• Athena Head Stud Kit

• Athena High-Performance Power Valves (cannot use OEM)

• All components brand new and covered by Athena’s warranty

📦 Fitment

• Yamaha YZ125 (2-stroke) 1997–2004

🛡️ Warranty Info

• Manufacturer warranty included

• Professional installation by a qualified technician is required

• Warranty does not cover failures caused by improper installation, tuning, misuse, or incorrect break-in procedures

🔑 Key Features

• Increases displacement from 125cc to 144cc for more power across the RPM range

• Aluminum cylinder with nickel-carbide coating for maximum durability

• High-performance anodized Athena power valves included (OEM valves will not work)

• Race-designed piston and gasket set for reliable compression and sealing

• Direct-fit kit with OEM-level reliability and service life