{"product_id":"wossner-8302db-piston-kit-2005-2021-yamaha-yz125-yz125x-standard-size-b","title":"Wossner 8302DB Piston Kit - 2005-2021 Yamaha YZ125 YZ125X Standard Size B","description":"\u003ch3\u003eWossner 8302DB Standard Series Forged 2-Stroke Piston Kit - Standard Size B\u003c\/h3\u003e\n\u003cp\u003eBring the power and precision back to your Yamaha small-bore engine with the Wossner 8302DB Piston Kit. Specifically engineered for the 2005-2021 Yamaha YZ125 and the 2020-2022 YZ125X, the \"Size B\" forged kit is the professional choice for riders performing their second or third top-end rebuild. At Moto-House MX, we know that as a 125cc cylinder sees more hours, the factory tolerances naturally loosen; this +0.01mm Size B kit provides the precise fitment needed to restore compression and eliminate piston rock in slightly worn bores.\u003c\/p\u003e\n\u003cp\u003eForged from high-performance aerospace aluminum alloy, the 8302DB is significantly stronger and more heat-resilient than stock cast pistons. It features a dual-ring configuration, which provides an exceptional secondary seal and improved heat dissipation—critical for 125cc engines that live in the high-RPM range. To ensure maximum longevity, Wossner applies a permanent molybdenum disulphide skirt coating that reduces friction and protects the cylinder wall. Precision-machined for 54.01mm bores, this 53.96mm piston ensures your YZ125 remains reliable and responsive on the track or trail.\u003c\/p\u003e\n\u003ch3\u003eTop Features: Wossner 8302DB Piston Kit\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cb\u003eStandard Size B (53.96mm):\u003c\/b\u003e Precision-machined for 54.01mm bores to compensate for minor cylinder wear and restore factory-correct clearances.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eDual Ring Configuration:\u003c\/b\u003e Enhances cylinder sealing and cooling efficiency, helping to maintain consistent power throughout long motos.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eAerospace-Grade Forging:\u003c\/b\u003e Built to withstand high-RPM stress and thermal expansion far better than original cast alternatives.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eLow-Friction Skirt Coating:\u003c\/b\u003e Permanent skirt treatment minimizes drag and piston rock for a quieter, smoother running engine and extended cylinder life.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eOptimized Lightness:\u003c\/b\u003e Expertly machined to reduce reciprocating mass, ensuring the YZ125 retains its signature snappy throttle response.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eComplete Assembly:\u003c\/b\u003e Includes the forged Size B piston, high-performance rings, wrist pin, and circlips.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cb\u003eExpert Pro-Tip:\u003c\/b\u003e The Yamaha YZ125 is a high-performance machine that relies on perfect piston-to-wall clearance for maximum power. If your cylinder has 30-50 hours of ride time, stepping up to a Wossner Size B (53.96mm) is the standard expert method to bring your mechanical tolerances back to ideal levels. Always use a precision bore gauge to confirm your cylinder measures 54.01mm before installation. For a professional-grade rebuild, always install with a fresh top-end gasket kit and utilize premium 2-stroke oil to protect your forged assembly.\u003c\/p\u003e\n\u003ch3\u003eFitment List\u003c\/h3\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse;\" cellpadding=\"8\" border=\"1\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eYear Range\u003c\/th\u003e\n\u003cth\u003eVehicle Brand\u003c\/th\u003e\n\u003cth\u003eVehicle Model\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e2005-2021\u003c\/td\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003eYZ125\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2020-2022\u003c\/td\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003eYZ125X\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003e\u003cb\u003eQ: When should I choose Size B instead of Size A?\u003c\/b\u003e\u003cbr\u003eA: Size B (53.96mm) is 0.01mm larger than Size A. It is used when the cylinder bore has worn slightly larger than the original 54.00mm, ensuring you maintain the tight seal necessary for peak horsepower.\u003c\/p\u003e\n\u003cp\u003e\u003cb\u003eQ: Is this kit compatible with the YZ125X off-road model?\u003c\/b\u003e\u003cbr\u003eA: Yes, this kit is specifically designed to fit both the YZ125 motocross bike and the YZ125X cross-country model within the specified year ranges.\u003c\/p\u003e\n\u003cp\u003e\u003cb\u003eQ: Do forged pistons require a different break-in process?\u003c\/b\u003e\u003cbr\u003eA: Forged pistons expand differently than cast pistons. It is recommended to perform 2-3 heat cycles, allowing the engine to cool completely between each, before riding at full race pace.\u003c\/p\u003e\n\u003ch3\u003eRecommended Pairings\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cb\u003eComplete Top End Gasket Set:\u003c\/b\u003e Ensure a leak-free rebuild and maintain correct squish heights with fresh gaskets.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eMotul 800 2T Factory Line:\u003c\/b\u003e High-performance lubricant to keep your new forged piston protected in high-RPM racing conditions.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eRestore your machine’s power and precision today. Buy now at Moto-House MX!\u003c\/p\u003e\n\u003cp\u003e\u003cb\u003eMoto-House MX – Choice of Champions\u003c\/b\u003e – is located in Clermont\/Montverde, FL. The Best Motocross\/UTV \u0026amp; ATV Shop in Central Florida. Stop by our local store in Montverde, FL or enjoy lightning-fast shipping across the USA.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"WOSSNER","offers":[{"title":"Default Title","offer_id":44495995437139,"sku":"8302DB","price":132.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1754\/5421\/files\/2894188.png?v=1776229816","url":"https:\/\/motohousemx.com\/products\/wossner-8302db-piston-kit-2005-2021-yamaha-yz125-yz125x-standard-size-b","provider":"Moto-House MX","version":"1.0","type":"link"}