This 300cc Big Bore Kit by Athena increases YZ250 displacement to 293cc. Cylinder is nickel-carbide plated with enlarged water passages for exceptional durability and performance. Bore increased to 72mm (stock is 66.4mm); stroke remains the same as stock (72mm). 15:1 compression ratio. Forged, domed piston. No case machining necessary.
Kit includes:
* Cylinder * Head * Piston * Rings * Pin * Clips * Power valve assembly * All required gaskets
Fits:
- 2009 – 2016 YZ250
- 2016 YZ250X