{"product_id":"namura-top-end-kit-83-5-mm-0-50-mm-11-1-compression-for-yamaha-yfm400","title":"NAMURA Top End Kit 83.5 mm, +0.50 mm, 11:1 Compression for Yamaha YFM400","description":"\u003cp\u003eRestore reliable top-end performance with the NAMURA Top End Kit, manufacturer part number NA-40006-2K. This 83.5 mm, +0.50 mm oversize kit is designed for select Yamaha 400cc ATV applications and includes the essential components needed for a complete top-end rebuild. The kit includes a piston, piston rings, wrist pin, circlips, top-end bearing, and gasket kit.\u003c\/p\u003e\u003cp\u003eBuilt for durability and consistent engine operation, the piston uses a hypereutectic casting process with increased silicon content. This construction helps reduce thermal expansion, improve wear resistance, and withstand higher cylinder temperatures. The 11:1 compression design supports strong combustion performance when used with the correct engine setup and fuel requirements.\u003c\/p\u003e\u003cp\u003eThe piston features MOS2, or Teflon\/Molybdenum, coated skirts applied through a rolled-on process for a strong, durable bond. This coating helps reduce friction, improve heat transfer, and minimize the risk of cold seizures. Machined smooth heads help reflect combustion heat and reduce carbon buildup, while the anodized dome improves heat resistance and piston durability.\u003c\/p\u003e\u003cp\u003eThis NAMURA top-end kit fits 2000–2006 Yamaha YFM400FB Big Bear 4WD models with SRA suspension and 1993–1995 Yamaha YFM400FA Kodiak 4WD models with SRA suspension. Verify the model year, engine configuration, bore specification, and required oversize before installation. Manufacturer part number: NA-40006-2K. Vendor part number: 186-40062.\u003c\/p\u003e\u003cp\u003e\u003cb\u003eFeatures:\u003c\/b\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eComplete top-end kit: Includes piston, rings, wrist pin, circlips, top-end bearing, and gasket kit\u003c\/li\u003e\n\u003cli\u003e83.5 mm bore size: +0.50 mm oversize specification for compatible Yamaha 400cc engine rebuilds\u003c\/li\u003e\n\u003cli\u003e11:1 compression ratio: Designed to support strong combustion performance with compatible engine configurations\u003c\/li\u003e\n\u003cli\u003eMOS2-coated piston skirts: Helps reduce friction, improve heat transfer, and minimize cold-seizure risk\u003c\/li\u003e\n\u003cli\u003eMachined smooth piston head: Helps reflect combustion heat and reduce carbon buildup\u003c\/li\u003e\n\u003cli\u003eAnodized piston dome: Provides increased heat resistance and durability\u003c\/li\u003e\n\u003cli\u003eHypereutectic construction: Increased silicon content helps reduce expansion and improve wear resistance\u003c\/li\u003e\n\u003cli\u003eFitment: Fits 2000–2006 Yamaha YFM400FB Big Bear 4WD SRA and 1993–1995 Yamaha YFM400FA Kodiak 4WD SRA models\u003c\/li\u003e\n\u003cli\u003eBrand: NAMURA\u003c\/li\u003e\n\u003cli\u003eManufacturer part number: NA-40006-2K\u003c\/li\u003e\n\u003cli\u003eVendor part number: 186-40062\u003c\/li\u003e\n\u003c\/ul\u003e\u003cbr\u003e\nFitment:\u003cbr\u003e\n1993 Yamaha YFM400FA Kodiak 4WD [SRA]\u003cbr\u003e\n1994 Yamaha YFM400FA Kodiak 4WD [SRA]\u003cbr\u003e\n1995 Yamaha YFM400FA Kodiak 4WD [SRA]\u003cbr\u003e\n1996 Yamaha YFM400FA Kodiak 4WD [SRA]\u003cbr\u003e\n1997 Yamaha YFM400FA Kodiak 4WD [SRA]\u003cbr\u003e\n1998 Yamaha YFM400FA Kodiak 4WD [SRA]\u003cbr\u003e\n1999 Yamaha YFM400FA Kodiak 4WD [SRA]\u003cbr\u003e\n2000 Yamaha YFM400 Big Bear 2WD [SRA]\u003cbr\u003e\n2000 Yamaha YFM400FB Big Bear 4WD [SRA]\u003cbr\u003e\n2001 Yamaha YFM400 Big Bear 2WD [SRA]\u003cbr\u003e\n2001 Yamaha YFM400FB Big Bear 4WD [SRA]\u003cbr\u003e\n2002 Yamaha YFM400 Big Bear 2WD [SRA]\u003cbr\u003e\n2002 Yamaha YFM400FB Big Bear 4WD [SRA]\u003cbr\u003e\n2003 Yamaha YFM400 Big Bear 2WD [SRA]\u003cbr\u003e\n2003 Yamaha YFM400FB Big Bear 4WD [SRA]\u003cbr\u003e\n2004 Yamaha YFM400 Big Bear 2WD [SRA]\u003cbr\u003e\n2004 Yamaha YFM400FB Big Bear 4WD [SRA]\u003cbr\u003e\n2005 Yamaha YFM400FB Big Bear 4WD [SRA]\u003cbr\u003e\n2006 Yamaha YFM400FB Big Bear 4WD [SRA]\u003cbr\u003e\n2007 Yamaha YFM400FBI Big Bear 4WD [IRS]\u003cbr\u003e\n2008 Yamaha YFM400FBI Big Bear 4WD [IRS]\u003cbr\u003e\n2009 Yamaha YFM400FBI Big Bear 4WD [IRS]\u003cbr\u003e\n2010 Yamaha YFM400FBI Big Bear 4WD [IRS]","brand":"NAMURA","offers":[{"title":"Default Title","offer_id":67559045857515,"sku":"186-40062","price":122.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0611\/3882\/9547\/files\/dd77-572a583cd9540_be42b285-cadd-4757-b88c-ddc3b84ce6c6.jpg?v=1790769845","url":"https:\/\/ctracingservices.com\/products\/namura-top-end-kit-83-5-mm-0-50-mm-11-1-compression-for-yamaha-yfm400","provider":"Cascade Tire \u0026 Racing Services","version":"1.0","type":"link"}