Keeway RKS 125 57mm Cylinder & Piston Kit – 157FMI Type
Brand-new unbranded standard 57 mm cylinder, piston, ring and gasket kit for compatible Keeway RKS 125 applications using the 157FMI GS-style engine family.
Key Specifications
- Standard bore: 57 mm
- Engine family: K157FMI / 157FMI GS-style
- Stroke reference: 48.8 mm where documented
- Piston-pin reference: 14 mm
- Air-cooled single-cylinder 4-stroke application
- EGR / secondary-air-system style cylinder family
- Condition: Brand new
- Type: Unbranded aftermarket replacement
What's Included
- 1 x cylinder barrel
- 1 x piston
- 1 x piston ring set
- Head and base gaskets
Vehicle Compatibility
| Model | Years / Variant | Notes |
|---|---|---|
| RKS 125 / RKS Classic | 2011–2017 | OEM cylinder 139013210030; 57 mm / 14 mm piston family |
| RKS 125 EFI / RKS Sport EFI | 2017–2020 verified | 57 mm / 14 mm piston family; compare OEM cylinder revision and secondary-air ports |
Important Fitment Information
Keeway RKS engines are documented as 157FMI-2A/2B rather than every version being stamped exactly K157FMI. The critical top-end evidence is the 57 mm bore, 14 mm piston pin and matching EGR/secondary-air cylinder layout. Compare the original cylinder before ordering.
Do not order by 125cc capacity alone. Compare bore, piston-pin diameter, piston crown, cylinder height, stud spacing, gasket profile, oil passages and EGR/secondary-air ports with the original top end.
Installation
Correct piston-ring orientation, piston direction, valve timing, gasket installation and cylinder-head torque are essential. Professional installation is recommended where the correct engine-building procedure is not known.