{"product_id":"keith-black-pistons-std-flat-top-pistons-kb258-std-for-big-twin-1984-1999","title":"Keith Black Pistons Std Flat Top Pistons KB258.STD for Big Twin 1984-1999","description":"\u003cp style=\"margin:1em 0\"\u003eUpgrade your motorcycle's engine performance with Keith Black Pistons standard flat top pistons, engineered specifically for Harley-Davidson Big Twin Evolution engines. Crafted from a high-grade hypereutectic 16% silicon cast alloy, these pistons provide exceptional thermal stability and a low expansion rate, allowing for tighter piston-to-cylinder operating clearances in air-cooled applications.\u003c\/p\u003e\u003cp style=\"margin:1em 0\"\u003eDelivering an 8.6:1 compression ratio with standard 80cc combustion chambers, this piston set delivers durable reliability and smooth power output. The complete package includes two pistons, rings, wrist pins, and spiral locks to support a direct-fit OEM replacement.\u003c\/p\u003e\n\u003ch3 style=\"margin:1.25em 0 0.5em\"\u003eKey Features\u003c\/h3\u003e\n\u003ctable class=\"pu-table\" style=\"width:100%;border-collapse:separate;border-spacing:0;border:0;box-shadow:none;outline:none;background:none;table-layout:fixed;margin:0 0 1em\"\u003e\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eBrand\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eKeith Black Pistons\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eManufacturer Part Number\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eKB258.STD\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eProduct Type\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eEngine Pistons\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003ePiston Top Style\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eFlat Top\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eBore Size\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003e88.8 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eStroke\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003e108 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eCompression Ratio\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003e8.6:1 (with 80cc chamber volume)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eMaterial\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eHypereutectic Alloy (16% Silicon)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003eReplaces OEM Number\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003e21940-83\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"border:0;padding:0.4em 0.75em 0.4em 0;opacity:0.65;vertical-align:top\"\u003eEstimated Weight\u003c\/td\u003e\n\u003ctd style=\"border:0;padding:0.4em 0;vertical-align:top\"\u003e1.5 kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\u003c\/table\u003e\n\u003ch3 style=\"margin:1.25em 0 0.5em\"\u003eHighlights\u003c\/h3\u003e\n\u003cul style=\"margin:1em 0\"\u003e\n\u003cli\u003eEngineered from 16% silicon hypereutectic alloy for low thermal expansion\u003c\/li\u003e\n\u003cli\u003eIdeal for air-cooled Big Twin Evolution motors\u003c\/li\u003e\n\u003cli\u003eProvides an 8.6:1 compression ratio with 80cc heads\u003c\/li\u003e\n\u003cli\u003eDirect replacement for OEM # 21940-83\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3 style=\"margin:1.25em 0 0.5em\"\u003eCompatibility\u003c\/h3\u003e\n\u003cp style=\"margin:1em 0\"\u003eFits Harley-Davidson Big Twin Evolution (Evo) engine models from 1984 through 1999.\u003c\/p\u003e\n\u003ch3 style=\"margin:1.25em 0 0.5em\"\u003eWhat's included\u003c\/h3\u003e\n\u003cul style=\"margin:1em 0\"\u003e\n\u003cli\u003e2 x Keith Black Hypereutectic Pistons\u003c\/li\u003e\n\u003cli\u003e1 x Set of Piston Rings\u003c\/li\u003e\n\u003cli\u003e2 x Wrist Pins\u003c\/li\u003e\n\u003cli\u003e4 x Pin Retaining Clips\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3 style=\"margin:1.25em 0 0.5em\"\u003eDownloads\u003c\/h3\u003e\n\u003cul style=\"margin:1em 0\"\u003e\u003cli style=\"margin:0 0 0.35em\"\u003e\u003ca href=\"https:\/\/images.rolliesspeedshop.com\/pdf\/KB258.STD.pdf\" target=\"_blank\" rel=\"noopener nofollow\"\u003eDownload Product information ( PDF)\u003c\/a\u003e\u003c\/li\u003e\u003c\/ul\u003e\n\u003ctable class=\"pu-table\" style=\"width:100%;border-collapse:separate;border-spacing:0;border:0;box-shadow:none;outline:none;background:none;table-layout:fixed;margin:0\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd style=\"border:0;padding:0\"\u003e\n\u003ch3 style=\"margin:1.25em 0 0.5em\"\u003eFrequently asked questions\u003c\/h3\u003e\n\u003cstyle\u003e.pu-faq[open]\u003esummary .pu-faq-c{transform:rotate(180deg)}\u003c\/style\u003e\n\u003ctable class=\"pu-table\" style=\"width:100%;border-collapse:separate;border-spacing:0;border:0;box-shadow:none;outline:none;background:none;table-layout:fixed;margin:0 0 1em\"\u003e\u003ctbody\u003e\n\u003ctr\u003e\u003ctd style=\"border:0;padding:0;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003e\u003cdetails class=\"pu-faq\" style=\"padding:0.45em 0\"\u003e\u003csummary style=\"cursor:pointer;display:flex;align-items:center;justify-content:space-between;gap:10px;list-style:none\"\u003e\u003cstrong\u003eWhat is the compression ratio of these pistons?\u003c\/strong\u003e\u003csvg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewbox=\"0 0 24 24\" width=\"18\" height=\"18\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"1.75\" stroke-linecap=\"round\" stroke-linejoin=\"round\" class=\"pu-faq-c\" style=\"width:1em;height:1em;flex:none;opacity:0.6;transition:transform 0.15s\" aria-hidden=\"true\"\u003e\u003cpath d=\"M6 9l6 6l6 -6\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\u003c\/summary\u003e\u003cp style=\"margin:0.4em 0 0\"\u003eThese pistons provide an 8.6:1 compression ratio when used with an 80cc cylinder head chamber volume.\u003c\/p\u003e\u003c\/details\u003e\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd style=\"border:0;padding:0;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003e\u003cdetails class=\"pu-faq\" style=\"padding:0.45em 0\"\u003e\u003csummary style=\"cursor:pointer;display:flex;align-items:center;justify-content:space-between;gap:10px;list-style:none\"\u003e\u003cstrong\u003eWhat components are included in the kit?\u003c\/strong\u003e\u003csvg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewbox=\"0 0 24 24\" width=\"18\" height=\"18\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"1.75\" stroke-linecap=\"round\" stroke-linejoin=\"round\" class=\"pu-faq-c\" style=\"width:1em;height:1em;flex:none;opacity:0.6;transition:transform 0.15s\" aria-hidden=\"true\"\u003e\u003cpath d=\"M6 9l6 6l6 -6\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\u003c\/summary\u003e\u003cp style=\"margin:0.4em 0 0\"\u003eThe complete kit includes two pistons, piston rings, wrist pins, and clips.\u003c\/p\u003e\u003c\/details\u003e\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd style=\"border:0;padding:0;border-bottom:1px solid rgba(128,128,128,0.16);border-bottom:1px solid color-mix(in srgb,currentColor 12%,transparent)\"\u003e\u003cdetails class=\"pu-faq\" style=\"padding:0.45em 0\"\u003e\u003csummary style=\"cursor:pointer;display:flex;align-items:center;justify-content:space-between;gap:10px;list-style:none\"\u003e\u003cstrong\u003eWhat material is used to construct these pistons?\u003c\/strong\u003e\u003csvg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewbox=\"0 0 24 24\" width=\"18\" height=\"18\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"1.75\" stroke-linecap=\"round\" stroke-linejoin=\"round\" class=\"pu-faq-c\" style=\"width:1em;height:1em;flex:none;opacity:0.6;transition:transform 0.15s\" aria-hidden=\"true\"\u003e\u003cpath d=\"M6 9l6 6l6 -6\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\u003c\/summary\u003e\u003cp style=\"margin:0.4em 0 0\"\u003eThey are cast from a hypereutectic alloy featuring a 16% silicon content, designed for low thermal expansion in air-cooled engines.\u003c\/p\u003e\u003c\/details\u003e\u003c\/td\u003e\u003c\/tr\u003e\n\u003ctr\u003e\u003ctd style=\"border:0;padding:0\"\u003e\u003cdetails class=\"pu-faq\" style=\"padding:0.45em 0\"\u003e\u003csummary style=\"cursor:pointer;display:flex;align-items:center;justify-content:space-between;gap:10px;list-style:none\"\u003e\u003cstrong\u003eWhat OEM part number does this set replace?\u003c\/strong\u003e\u003csvg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewbox=\"0 0 24 24\" width=\"18\" height=\"18\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"1.75\" stroke-linecap=\"round\" stroke-linejoin=\"round\" class=\"pu-faq-c\" style=\"width:1em;height:1em;flex:none;opacity:0.6;transition:transform 0.15s\" aria-hidden=\"true\"\u003e\u003cpath d=\"M6 9l6 6l6 -6\"\u003e\u003c\/path\u003e\u003c\/svg\u003e\u003c\/summary\u003e\u003cp style=\"margin:0.4em 0 0\"\u003eThis kit directly replaces OEM part number 21940-83.\u003c\/p\u003e\u003c\/details\u003e\u003c\/td\u003e\u003c\/tr\u003e\n\u003c\/tbody\u003e\u003c\/table\u003e\n\u003c\/td\u003e\u003c\/tr\u003e\u003c\/tbody\u003e\u003c\/table\u003e","brand":"Keith Black Pistons","offers":[{"title":"Default Title","offer_id":49680784556288,"sku":"KB258.STD","price":566.15,"currency_code":"NZD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0855\/0888\/2688\/files\/KB258.STD.jpg?v=1788494182","url":"https:\/\/baychoppers.co.nz\/products\/keith-black-pistons-std-flat-top-pistons-kb258-std-for-big-twin-1984-1999","provider":"Bay Choppers NZ","version":"1.0","type":"link"}