Big Bore Kit 72mm 293cc – Yamaha 99-21 YZ250

Big bore kit for 1999 to 2021 Yamaha YZ250. 293cc. Includes cylinder, cylinder head, piston kit w/rings, power valve and top end gasket. Made with larger water jackets for greater cooling capacity. Ported power valves for more power and torque over the stock YZ250. Kit was made to be a improvement over the Athena YZ293 big bore. Improved power valve porting and uses factory style flat metal gaskets for increased reliability over the rubber o-ring Athena gaskets.

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