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, and all required gaskets. YZ models are for closed course
competition regardless of modification
Fits '03-'17 YZ250; '16-'17 YZ250X
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Cycle Sport Yamaha
8544 E Ridge Road (US 6)
Hobart, IN 46342
Toll Free: 866-6YAMAHA