{"product_id":"piston-kit-yamaha-yfm-660-grizzly-rhino-raptor-os-1-50","title":"OS 1.50 Piston Kit For Yamaha YFM 660 Grizzly 2002 2007 Rhino 2002 2007 Raptor 2002 2007 OEM Replacement","description":"\u003cdiv\u003e\n\u003cp\u003eThis OS 1.50 oversize piston kit is a purpose-built aftermarket replacement designed for the Yamaha YFM660 engine family used in Grizzly, Rhino, and Raptor models from the early 2000s. It’s engineered to restore peak compression and improve throttle response during rebuilds, performance tune-ups, or trail-ready upgrades. The oversize bore feature increases displacement potential, delivering stronger torque and more responsive power delivery when paired with proper clearances and matching components.\u003c\/p\u003e\n\u003cp\u003eBuilt for reliability in demanding terrain, this OS 1.50 piston kit provides a cost-effective solution for riders who push their 660cc engines on trails or in farm work. By returning the engine to its designed compression and reduction of oil consumption associated with worn pistons and rings, this aftermarket kit helps restore consistent power, smoother acceleration, and longer service intervals between major rebuilds. It’s a practical choice for riders who refuse to compromise on performance while avoiding OEM pricing.\u003c\/p\u003e\n\u003ch3\u003eComprehensive Vehicle Fitment\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eManufacturer\u003c\/th\u003e\n\u003cth\u003eModels \/ Series\u003c\/th\u003e\n\u003cth\u003eYears \/ Details\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003eYFM660 Grizzly\u003c\/td\u003e\n\u003ctd\u003e2002–2007 (660cc single-cylinder engine; various bore variants by model year)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003eYFM660 Rhino\u003c\/td\u003e\n\u003ctd\u003e2002–2007 (660cc engine family; later Rhino variations documented in industry references)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYamaha\u003c\/td\u003e\n\u003ctd\u003eYFM660R Raptor\u003c\/td\u003e\n\u003ctd\u003e2002–2007 (660cc performance-focused variant)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003e\u003c\/h3\u003e\n\u003ch3\u003eProduct Specifications\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eAttribute\u003c\/th\u003e\n\u003cth\u003eDetails\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eOEM Reference Part Numbers\u003c\/td\u003e\n\u003ctd\u003eN\/A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003ePiston Kit OS 1.50\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eAftermarket Replacement\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApplication\u003c\/td\u003e\n\u003ctd\u003eYamaha YFM660 Grizzly, Rhino, and Raptor engines (2002–2007)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBore Size (Oversize)\u003c\/td\u003e\n\u003ctd in=\"\"\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eStock Bore (Reference)\u003c\/td\u003e\n\u003ctd for=\"\"\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eStroke\u003c\/td\u003e\n\u003ctd\u003e84.0 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003e\u003c\/h3\u003e\n\u003ch3\u003eOEM \u0026amp; Aftermarket Cross-Reference Information\u003c\/h3\u003e\n\u003ctable style=\"width: 100%;\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth style=\"width: 17.4897%;\"\u003ePart Number\u003c\/th\u003e\n\u003cth style=\"width: 17.1674%;\"\u003eBrand \/ Type\u003c\/th\u003e\n\u003cth style=\"width: 64.6209%;\"\u003eCross-Reference Notes\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 17.4897%;\"\u003e4966M10000\u003c\/td\u003e\n\u003ctd style=\"width: 17.1674%;\"\u003eWiseco Armorglide (Aftermarket)\u003c\/td\u003e\n\u003ctd style=\"width: 64.6209%;\"\u003eFits Yamaha YFM660FG Grizzly (2002–2008), YXR660F Rhino (2005–2007), YFM660R Raptor (2001–2005); standard bore 100.00 mm; used as cross-reference for equivalent performance pistons.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 17.4897%;\"\u003e4737M10050\u003c\/td\u003e\n\u003ctd style=\"width: 17.1674%;\"\u003eWiseco\u003c\/td\u003e\n\u003ctd style=\"width: 64.6209%;\"\u003eHigh-performance piston kit for YFM660 variants; indicates oversize compatibility (11:1 CR; various YFM660 applications such as Grizzly\/Raptor\/Rhino); used as aftermarket cross-reference for comparable 660cc engines.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003e\u003c\/h3\u003e\n\u003ch3\u003eWhat's Included\u003c\/h3\u003e\n\u003cp\u003eThe OS 1.50 Piston Kit ships with the essential components for a top-end refresh:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cb\u003ePiston\u003c\/b\u003e (OS 1.50 oversize bore)\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003ePiston Rings\u003c\/b\u003e (ring set)\u003c\/li\u003e\n\u003cli\u003e\u003cb\u003ePiston Pin\u003c\/b\u003e\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eCirclips\u003c\/b\u003e (piston pin retainers)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cem\u003eNote: Related gaskets (head, base, and cylinder o-rings) and ancillary hardware are not included unless specified elsewhere.\u003c\/em\u003e\u003c\/p\u003e\n\u003ch3\u003eWhy Choose This Aftermarket Replacement?\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cb\u003eDirect-Fit Compatibility:\u003c\/b\u003e Engineered to align with Yamaha YFM660 Grizzly, Rhino, and Raptor end-user rebuilds without aftermarket-system guesswork.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eOEM Cross-Reference:\u003c\/b\u003e Backed by cross-reference options from established aftermarket brands to support value-conscious rebuilds.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eOversize Bore Advantage:\u003c\/b\u003e OS 1.50 oversize increases displacement, contributing to improved torque and throttle response when paired with proper clearances.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003ePremium Endurance Concepts:\u003c\/b\u003e Built with robust piston-to-cylinder interface and plating considerations that favor long-lasting wear resistance in 660cc engines.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003ePerformance Restoration:\u003c\/b\u003e Restores compression and consistent power delivery after piston and ring wear, helping you reclaim original mid-range punch and hill-climbing ability.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eCost-Effective Rebuild Solution:\u003c\/b\u003e A practical alternative to OEM pricing while delivering reliable end-user service life for trail and farm use.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eInstallation Notes:\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eMeasure the engine bore to confirm stock size and verify whether an OS 1.50 bore is appropriate for your cylinder; stock bores in this family commonly run around 100.0 mm, with some variants at 102 mm in other model variants. This verification ensures correct piston-to-wall clearance.\u003c\/li\u003e\n\u003cli\u003ePre-lubricate the piston rings and skirt with assembly lube before installation to prevent dry-start wear and ensure proper seating during first startup.\u003c\/li\u003e\n\u003cli\u003eInstall the piston with the correct orientation and align ring gaps away from the piston pin and crank journals; stagger ring gaps by approximately 120 degrees for uniform sealing.\u003c\/li\u003e\n\u003cli\u003eInspect the cylinder bore for scoring or lacquer; if bore wear is present, bore and hone as needed to maintain straightness and crosshatch pattern for ring seating.\u003c\/li\u003e\n\u003cli\u003eCheck the wrist pin fitment and circlips; ensure circlips are fully seated and secure to prevent wrist pin migration under load.\u003c\/li\u003e\n\u003cli\u003eReplace associated gaskets and seals (head and base gaskets) during the top-end refresh to maintain proper compression and oil sealing; verify torque specs from your service manual for any fasteners encountered during installation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eWhy Upgrade?\u003c\/h3\u003e\n\u003cp\u003eRunning a worn piston kit on a 660cc Yamaha engine can lead to a progressive loss of compression, reduced power, higher oil consumption, and degraded throttle response under load. Upgrading to this OS 1.50 piston kit restores compression, boosts torque, and improves overall reliability for trail-riding and farm-duty scenarios, returning the engine to a more predictable and responsive character.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"ATV City","offers":[{"title":"Default Title","offer_id":57319261176182,"sku":"190.40004-6","price":133.26,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0971\/0302\/0406\/files\/image_2026-02-25_214459139.png?v=1772055907","url":"https:\/\/dgtagri.co.uk\/products\/piston-kit-yamaha-yfm-660-grizzly-rhino-raptor-os-1-50","provider":"DGT Agri","version":"1.0","type":"link"}