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