{"product_id":"wossner-8330db-piston-kit-2002-2026-yamaha-yz85-standard-size-b","title":"Wossner 8330DB Piston Kit - 2002-2026 Yamaha YZ85 Standard Size B","description":"\u003ch3\u003eWossner 8330DB Standard Series Forged 2-Stroke Piston Kit - Standard Size B\u003c\/h3\u003e\n\n\u003cp\u003eMaintain the competitive edge of your mini-racer with the Wossner 8330DB Piston Kit. Tailored specifically for the 2002-2026 Yamaha YZ85, the \"Size B\" piston is the professional's choice for engines that have seen some track time. At Moto-House MX, we understand that as a cylinder wears, factory \"Size A\" clearances can become too loose; this +0.01mm Size B kit provides the precise fitment needed to restore compression and eliminate piston slap in slightly worn bores.\u003c\/p\u003e\n\n\u003cp\u003eForged from high-grade aerospace aluminum alloy, the 8330DB is built to withstand the punishing RPMs of 85cc motocross competition. The dual-ring design is a key feature for the YZ85, offering improved secondary compression and superior heat transfer to the cylinder wall, which helps maintain power throughout long, hot motos. To ensure longevity, Wossner applies a permanent molybdenum disulphide skirt coating that reduces friction and protects the cylinder during high-stress operation. With optimized machining for a perfect strength-to-weight ratio, this 47.46mm piston ensures your YZ85 retains its legendary throttle response while gaining the durability of a forged component.\u003c\/p\u003e\n\n\u003ch3\u003eTop Features: Wossner 8330DB Piston Kit\u003c\/h3\u003e\n\u003cul\u003e\n    \u003cli\u003e\n\u003cb\u003eStandard Size B (47.46mm):\u003c\/b\u003e Specifically designed for 47.51mm bores, providing a tighter fit for cylinders with slight wear to restore peak performance.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cb\u003eDual Ring Configuration:\u003c\/b\u003e Enhances cylinder sealing and cooling, ensuring consistent power delivery for demanding mini-moto racers.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cb\u003eAerospace-Grade Forging:\u003c\/b\u003e Offers superior structural integrity compared to stock cast pistons, significantly reducing the risk of skirt failure at high RPM.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cb\u003eLow-Friction Skirt Coating:\u003c\/b\u003e Permanent coating reduces internal drag and piston rock for a quieter running engine and longer service life.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cb\u003ePrecision Lightness:\u003c\/b\u003e Engineered to minimize reciprocating mass, allowing the engine to rev freely and respond instantly to rider input.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cb\u003eComplete Top-End Kit:\u003c\/b\u003e Includes the forged Size B piston, performance rings, wrist pin, and circlips.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cb\u003eExpert Pro-Tip:\u003c\/b\u003e When your YZ85 has 20-30 hours of hard riding, the cylinder bore often grows by a fraction of a millimeter. Stepping up to a Wossner Size B (47.46mm) is the standard practice for top-tier mechanics to bring the piston-to-wall clearance back to ideal specifications without needing a full replate. Always measure your cylinder with a bore gauge to confirm that 47.51mm is your current size. For the best results, install with a fresh top-end gasket kit and use premium 2-stroke oil to protect your investment.\u003c\/p\u003e\n\n\u003ch3\u003eFitment List\u003c\/h3\u003e\n\u003ctable border=\"1\" cellpadding=\"8\" style=\"width: 100%; border-collapse: collapse;\"\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\u003e2002-2026\u003c\/td\u003e\n            \u003ctd\u003eYamaha\u003c\/td\u003e\n            \u003ctd\u003eYZ85 \/ YZ85LW (Large Wheel)\u003c\/td\u003e\n        \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003e\u003cb\u003eQ: When should I use a Size B piston instead of Size A?\u003c\/b\u003e\u003cbr\u003e\nA: Size B (47.46mm) is used when your cylinder has minor wear. If your standard 47.50mm bore has increased slightly toward 47.51mm, the Size B provides the correct clearance to prevent power loss and excessive piston movement.\u003c\/p\u003e\n\n\u003cp\u003e\u003cb\u003eQ: Does a forged piston require a different break-in than a cast one?\u003c\/b\u003e\u003cbr\u003e\nA: Yes, forged pistons expand differently under heat. We recommend a couple of heat cycles followed by a progressive riding session to ensure the rings seat perfectly and the piston stabilizes within the bore.\u003c\/p\u003e\n\n\u003cp\u003e\u003cb\u003eQ: Is this kit compatible with the YZ85 Large Wheel?\u003c\/b\u003e\u003cbr\u003e\nA: Yes, the engine specifications for the YZ85 and YZ85LW are identical, and this kit fits both models perfectly.\u003c\/p\u003e\n\n\u003ch3\u003eRecommended Pairings\u003c\/h3\u003e\n\u003cul\u003e\n    \u003cli\u003e\n\u003cb\u003eComplete Top End Gasket Set:\u003c\/b\u003e Essential for maintaining proper squish clearance and a leak-free seal.\u003c\/li\u003e\n    \u003cli\u003e\n\u003cb\u003eYamalube 2-R Premix Oil:\u003c\/b\u003e Specifically formulated to protect high-performance Yamaha racing engines.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eRestore your machine’s power and precision today. Buy now at Moto-House MX!\u003c\/p\u003e\n\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\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n  \"@context\": \"https:\/\/schema.org\/\",\n  \"@type\": \"Product\",\n  \"name\": \"Wossner 8330DB Piston Kit\",\n  \"image\": [],\n  \"description\": \"Premium Wossner 8330DB Forged 2-Stroke Dual Ring Piston Kit for 2002-2026 Yamaha YZ85. 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