Athena 144cc Big Bore Cylinder Kit – Yamaha YZ125 / YZ125X (2005–2021) (P400485100030 / 68-4932)

Description

Unlock serious power with the Athena 58 mm Big Bore Cylinder Kit, designed to take your YZ125 or YZ125X to a full 144 cc displacement. This complete top-end package delivers crisp throttle response, stronger mid-range torque, and impressive over-rev for riders chasing podiums or premium trail performance.

Athena’s race-engineered cylinder features a nickel-carbide-plated aluminum bore, precision-matched to a forged 58 mm piston with a 14.0:1 compression ratio. Every kit includes the necessary gaskets, O-rings, and hardware for an easy bolt-on installation—no case machining required.

What’s Included

✅ 58 mm nickel-carbide-plated aluminum cylinder
✅ Forged high-compression piston (14.0:1 ratio)
✅ Complete top-end gasket & O-ring set
✅ Cylinder head insert and hardware
✅ Piston rings, wrist pin, and circlips
✅ Installation instructions

Fitment

📦 Fits:

• 2005–2021 Yamaha YZ125

• 2020–2021 Yamaha YZ125X

(Direct bolt-on big-bore conversion for stock YZ125 engines. No crankcase modification required.)

Key Features

• Boosts displacement from 125 cc → 144 cc

• 14.0:1 compression for explosive low-end and mid-range power

• Race-spec nickel-carbide plating for wear resistance

• CNC-machined head dome ensures uniform combustion

• Designed and tested by Athena Italy for MX and off-road racing

Warranty Info

Manufactured by Athena S.p.A., Italy.
Warranty and support handled directly through Athena.

Price & SKU

💲 Retail Price: $1,077.95
SKU: 68-4932 / P400485100030
Estimated Shipping Weight: 5.26 lb
Handling: Ships next business day