K157FMI 125cc 57 mm Cylinder Barrel & Piston Kit
Brand-new unbranded standard-bore top-end rebuild kit for selected air-cooled K157FMI / 157FMI GS-style 125cc engines using the matching 57 mm EGR/secondary-air-system cylinder configuration.
Key Specifications
- Engine family: K157FMI / 157FMI GS-style
- Displacement: Standard 125cc application
- Standard bore: 57 mm
- Engine stroke reference: 48.8 mm
- Piston-pin reference: 14 mm
- Cooling: Air-cooled
- Engine type: Single-cylinder 4-stroke
- Cylinder style: EGR / secondary-air-system type
- 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 / Engine Compatibility
| Make | Model / Engine | Years / Scope | Notes |
|---|---|---|---|
| Lexmoto | Adrenaline 125 / Adrenaline 125 EFI | K157FMI 57 x 48.8 mm engine family | Verify EGR ports and original cylinder |
| Lexmoto | Valiant 125 / Valiant 125 EFI | K157FMI 57 x 48.8 mm engine family | Verify EGR ports and original cylinder |
| Sinnis | Apache / Blade / Cafe / Max 2 / Retrostar / Scrambler / Stealth / Trackstar / Vista 125 | K157FMI applications | Model-year and emissions specification vary |
| Pulse / Superbyke | Adrenaline 125 / RMR125 | K157FMI applications | Match original cylinder and EGR arrangement |
Additional Verified Keeway Applications
The following Keeway applications use the same documented 57 mm / 14 mm GS-style top-end family. Engine suffixes and OEM cylinder revisions vary, so the original cylinder and EGR/secondary-air ports must still be compared before ordering.
| Keeway Model | Years / Variant | Fitment Notes |
|---|---|---|
| RKS 125 / RKS Classic | 2011–2017 | 157FMI-2B / GS-style 57 x 48.8 mm family; OEM cylinder 139013210030 on Euro 3 |
| RKS 125 EFI / RKS Sport EFI | 2017–2020 verified | 57 mm piston / 14 mm pin family; later OEM cylinder revisions exist |
| RKV 125 | 2011–2016 | 57 mm piston / 14 mm pin; OEM cylinder family 139013210030 |
| RKV 125 EFI / CBS EFI | 2017–2023 catalogued | 57 mm piston / 14 mm pin family; compare original cylinder revision |
| TX 125 Enduro / Supermoto | 2009–2017 | 157FMI-2B, 57 x 48.8 mm; OEM cylinder 139013210030 |
| TX 125 EFI Enduro / Supermoto | 2018–2020 | 57 mm piston / 14 mm pin family; compare EGR/SLS ports |
| Strike 125 | 2013–2014 documented | Explicitly catalogued as K157FMI; OEM cylinder 139013210030 and piston 179133090003 |
Important Fitment Information
The K157FMI engine family is well documented at 57 mm bore x 48.8 mm stroke, but not every K157FMI installation uses an identical cylinder or emissions arrangement. Check the EGR/secondary-air fittings and all physical dimensions against the existing parts before ordering.
Do not order by 125cc capacity alone. Before purchase, compare the original engine code, 57 mm bore, piston-pin diameter, piston crown/profile, cylinder height, stud spacing, gasket profile, oil passages and EGR/secondary-air ports with the existing engine.
The K157FMI family was used across carburetted and fuel-injected motorcycles, and production changes can affect top-end components. This kit should only be used where the original parts match the standard 57 mm K157FMI EGR-style configuration.
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.