Lexmoto LSM 125 K154FMI 57.4mm Big Bore Cylinder Piston Kit
Brand new aftermarket big-bore cylinder and piston kit for the Lexmoto LSM 125 (STR125YB) when fitted with its original K154FMI Yamaha/YBR-pattern engine.
Direct Fitment
- Lexmoto LSM 125 — STR125YB — K154FMI engine
Key Specification
- Nominal bore: 57.4 mm
- Piston pin: 15 mm
- Engine family: K154FMI / 154FMI Yamaha-YBR-pattern 125cc engine
- Cooling: Air-cooled
- Engine type: Single-cylinder, four-stroke
- Big-bore application: commonly marketed as a 150cc-style conversion
- Condition: Brand New aftermarket upgrade/rebuild part
- SKU: 00105-ENG
Why This Model Is Included
Lexmoto specifies the LSM 125 STR125YB with a K154FMI engine. Aftermarket YBR-pattern big-bore kits are specifically catalogued for 154FMI engines using the same general cylinder family and a 15 mm piston pin.
Important Compatibility Check
Do not order solely from the model name. Before fitting, compare the original cylinder and engine with the kit shown and confirm:
- K154FMI / compatible 154FMI engine code
- 15 mm piston pin
- Cylinder height and lower spigot dimensions
- Head-stud spacing
- Cam-chain tunnel position
- Oil-passage arrangement
- Base and head gasket profiles
- Crankcase opening clearance for the larger cylinder liner/spigot
Models Not Included
The Lexmoto Aspire 125 and ZSF 125 are not included in this listing. Lexmoto specifies those bikes with a 156FMI-3 YBR-style engine, including a different standard bore/stroke specification, so they should not be assumed to use this K154FMI/YBR big-bore kit.
Fuelling & Installation
A big-bore conversion changes airflow, compression and fuelling requirements. Carburettor jetting may require adjustment. Correct piston-ring orientation, cam timing, valve clearances, gasket preparation and running-in procedure are essential. Professional installation is recommended.
Road-Use Note
Increasing engine capacity can affect registration, insurance, licence entitlement and emissions compliance. The owner is responsible for confirming the legal requirements applicable to the motorcycle.
Shipping Estimate
Shopify shipping estimate: approximately 2.2 kg packed, with estimated parcel dimensions of 22 x 20 x 15 cm. Replace these estimates with measured packed weight and dimensions when available.