{"product_id":"athena-big-bore-cylinder-exhaust-valve-kit-72mm-bore-for-yamaha-yz250-2003-2026","title":"Athena Big Bore Cylinder \u0026 Exhaust Valve Kit 72mm Bore For Yamaha YZ250 2003-2026","description":"\u003cbr\u003e \u003cp\u003eThe Yamaha YZ 250 has long been a benchmark in motocross performance, delivering explosive power and unmatched agility. For riders seeking a radical upgrade, Athena introduces the \u003cstrong\u003eBig Bore Cylinder Kit\u003c\/strong\u003e, engineered to transform your YZ 250 into a race-ready powerhouse.\u003c\/p\u003e\u003cp\u003e\u003c\/p\u003e\u003ch3\u003eEngineered Evolution for Extreme Performance\u003c\/h3\u003e\u003cp\u003eThis latest version of the Big Bore kit marks a significant evolution over its predecessor. Every component has been redesigned and optimized to deliver \u003cstrong\u003emore horsepower, enhanced reliability, and sharper throttle response\u003c\/strong\u003e across the entire RPM range.\u003c\/p\u003e\u003cp\u003e\u003c\/p\u003e\u003ch3\u003eRedesigned Cylinder: New Port Timing, More Thrust\u003c\/h3\u003e\u003cp\u003eThe aluminum cylinder has been completely re-engineered with a \u003cstrong\u003enew port timing layout\u003c\/strong\u003e, designed to improve gas flow and maximize combustion efficiency. Internal geometries are optimized to deliver stronger mid-to-high RPM performance while maintaining smooth low-end power.\u003c\/p\u003e\u003cp\u003e\u003c\/p\u003e\u003ch3\u003eRecessed Head Design: Precision and Control\u003c\/h3\u003e\u003cp\u003eThe newly \u003cstrong\u003erecessed cylinder head\u003c\/strong\u003e is the result of advanced engineering. Improved shape and volume enhance squish and compression ratio, ensuring more efficient combustion and \u003cstrong\u003esmooth, controlled power delivery\u003c\/strong\u003e. The result is a more precise ride with instant throttle response.\u003c\/p\u003e\u003cp\u003e\u003c\/p\u003e\u003ch3\u003eCast Piston: Lightweight and High-Performance\u003c\/h3\u003e\u003cp\u003eThe new \u003cstrong\u003elightweight cast piston\u003c\/strong\u003e reduces reciprocating mass and improves engine responsiveness. This translates into quicker acceleration and reduced vibration, offering a cleaner and more aggressive riding experience.\u003c\/p\u003e\u003cp\u003e\u003c\/p\u003e\u003ch3\u003eOptimized Exhaust Valves: Aggressive Power, Smooth Torque\u003c\/h3\u003e\u003cp\u003eThe \u003cstrong\u003ecompletely redesigned exhaust valves\u003c\/strong\u003e contribute to a \u003cstrong\u003emore aggressive exhaust timing\u003c\/strong\u003e, delivering stronger top-end power while preserving low-end torque. This ensures \u003cstrong\u003eoptimal control and performance\u003c\/strong\u003e in every riding condition.\u003c\/p\u003e\u003cp\u003e\u003c\/p\u003e\u003ch3\u003eComplete Kit: Easy Installation, Total Reliability\u003c\/h3\u003e\u003cp\u003eAs with all Athena cylinder kits, the Big Bore kit includes a \u003cstrong\u003ehigh-quality gasket set\u003c\/strong\u003e, built to withstand the harshest racing conditions. Every component is designed for perfect sealing and long-lasting engine durability.\u003c\/p\u003e\u003cp\u003e\u003c\/p\u003e\u003ch2\u003eThe Ultimate Upgrade for Your Yamaha YZ 250\u003c\/h2\u003e\u003cp\u003eThe \u003cstrong\u003eAthena Big Bore Cylinder Kit for Yamaha YZ 250\u003c\/strong\u003e is more than just a replacement—it's a statement of raw power and uncompromising reliability. With this kit installed, every corner becomes an opportunity, and every twist of the throttle delivers pure adrenaline.\u003c\/p\u003e\u003cp\u003eWith Athena, your YZ 250 becomes the ultimate weapon on the track—ready to respond with surgical precision and unleash unstoppable force.\u003c\/p\u003e\u003cstrong\u003e\u003cp\u003eDescription:\u003c\/p\u003e\u003c\/strong\u003e\u003cul\u003e\n\u003cli\u003eRedesigned cylinder with new port timing\u003c\/li\u003e\n\u003cli\u003eRecessed head design for efficient combustion\u003c\/li\u003e\n\u003cli\u003eLightweight cast piston for better throttle response\u003c\/li\u003e\n\u003cli\u003eOptimized exhaust valves for aggressive power delivery\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003e\u003cstrong\u003eBrand: \u003c\/strong\u003eAthena\u003cbr\u003e\u003cstrong\u003ePart Number: \u003c\/strong\u003eP400485100104\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eFitment:\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\u003cli\u003eYamaha YZ250 2003-2026\u003c\/li\u003e\u003c\/ul\u003e\u003cbr\u003e\u003cp\u003e\u003cstrong\u003eNote: Image is for reference only, actual product may vary slightly.\u003c\/strong\u003e\u003c\/p\u003e","brand":"Athena","offers":[{"title":"Default Title","offer_id":45159771635791,"sku":"P400485100104-ATHENA-0426-ATH","price":1125.64,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0021\/7120\/7759\/files\/AthenaLogo_e9b0991b-f5ba-46a8-bae1-4b13de403a70.jpg?v=1777656855","url":"https:\/\/lionparts.com\/products\/athena-big-bore-cylinder-exhaust-valve-kit-72mm-bore-for-yamaha-yz250-2003-2026","provider":"Lionparts Powersports","version":"1.0","type":"link"}