Cylinder Head – YX 125 – 52.4mm

Genuine YX replacement cylinder head for 125cc pit bike engines. Designed to suit YX and Lifan engines running a 52.4mm piston – supplied fully assembled for a quick, no-fuss rebuild.

Specifications:

• ✅ Material: Aluminium alloy

• ✅ Piston Compatibility: 52.4mm only

• ✅ Valve Sizes: Inlet 23mm / Exhaust 20mm

• ✅ Cylinder Head Length: 91mm (machined face to machined face)

• ✅ Intake Port Diameter: 25mm

• ✅ Exhaust Port Diameter: 20mm

• ✅ Includes: Pre-installed camshaft, valves, and tappets

Fitment:

• ✅ Compatible Engines:

  • YX & Lifan 125cc engines

  • Typically, engine code 153FMI
    ⚠ The engine must have:
     - 52.4mm piston (not 54mm)
     - Alloy barrel (not black-painted steel type)
     - Valve inspection caps with a large 17mm nut
     - ❌ Not the caps with M6 screws on each side

Please Note:

• 🔧 Tappets must be set to: IN 0.10mm / EX 0.15mm during installation

• 🏁 Run-in required – ride at no more than 2/3 throttle for at least 2 hours to bed in valves properly

Built to match factory spec – ideal for restoring proper performance on YX and Lifan 125cc engines without second-guessing the fit.