{"product_id":"yamaha-yfz450r-debore-400cc","title":"YAMAHA YFZ450R DeBore","description":"\u003ch1\u003eYamaha YFZ450R 400cc De-Bore Conversion Kits \u0026amp; Components\u003c\/h1\u003e\n\u003cp\u003eThe \u003cstrong\u003eBNR Motorsports 400cc De-Bore Conversion Series\u003c\/strong\u003e is designed for riders looking to build a competitive and reliable 400cc Yamaha YFZ450R. Whether you're purchasing a complete conversion kit or replacement components, every part is engineered to work together for maximum performance.\u003c\/p\u003e\n\u003ch2\u003e\u003cspan\u003eSerialized Cylinder Identification\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp\u003e\u003cspan\u003eEvery BNR Motorsports 400cc de-bore cylinder is permanently engraved with a unique serial number for quality control and product traceability.\u003c\/span\u003e\u003c\/p\u003e\n\u003ch2\u003eImportant Information\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eAll Yamaha YFZ450R 400cc de-bore engines require a Vortex ECU programmed specifically for the 400cc conversion.\u003c\/strong\u003e The factory ECU cannot properly operate a de-bore engine because the fuel and ignition requirements are significantly different from a stock 450cc engine.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eIf you already own a Vortex ECU, you can send it to BNR Motorsports to be reflashed for your 400cc engine combination.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eIf you do not own a Vortex ECU, select the \u003cstrong\u003eKit with Vortex ECU\u003c\/strong\u003e option and we'll supply a new ECU that is custom programmed for your build.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eWhen ordering a Vortex ECU or ECU reflash, please provide your complete engine specifications, including camshaft, exhaust system, intake modifications, and any other performance upgrades. This allows us to create a calibration specifically for your ATV.\u003c\/p\u003e\n\u003ch2\u003e\u003cspan\u003eAvailable Options\u003c\/span\u003e\u003c\/h2\u003e\n\u003ch3\u003e\u003cspan\u003eComplete 400cc De-Bore Kit\u003c\/span\u003e\u003c\/h3\u003e\n\u003cp class=\"isSelectedEnd\"\u003e\u003cspan\u003eIncludes:\u003c\/span\u003e\u003c\/p\u003e\n\u003cdiv data-is-intersecting=\"true\" data-turn-id-container=\"request-WEB:c770b219-68b3-48e1-844a-1e36bc760abb-2\" class=\"\"\u003e\n\u003csection data-turn=\"assistant\" data-testid=\"conversation-turn-6\" data-turn-id-container=\"request-WEB:c770b219-68b3-48e1-844a-1e36bc760abb-2\" data-turn-id=\"request-WEB:c770b219-68b3-48e1-844a-1e36bc760abb-2\" dir=\"auto\" class=\"text-token-text-primary w-full focus:outline-none has-data-writing-block:pointer-events-none [\u0026amp;:has([data-writing-block])\u0026gt;*]:pointer-events-auto R6Vx5W_threadScrollVars scroll-mb-[calc(var(--scroll-root-safe-area-inset-bottom,0px)+var(--thread-response-height))] scroll-mt-[calc(var(--header-height)+min(200px,max(70px,20svh)))]\"\u003e\n\u003cdiv class=\"text-base my-auto mx-auto pb-10 [--thread-content-margin:var(--thread-content-margin-xs,calc(var(--spacing)*4))] @w-sm\/main:[--thread-content-margin:var(--thread-content-margin-sm,calc(var(--spacing)*6))] @w-lg\/main:[--thread-content-margin:var(--thread-content-margin-lg,calc(var(--spacing)*16))] px-(--thread-content-margin)\"\u003e\n\u003cdiv class=\"[--thread-content-max-width:40rem] @w-lg\/main:[--thread-content-max-width:48rem] mx-auto max-w-(--thread-content-max-width) flex-1 group\/turn-messages focus-visible:outline-hidden relative flex w-full min-w-0 flex-col agent-turn\" data-conversation-screenshot-content=\"\"\u003e\n\u003cdiv class=\"flex max-w-full flex-col gap-4 grow\"\u003e\n\u003cdiv data-turn-start-message=\"true\" class=\"min-h-8 text-message relative flex w-full flex-col items-end gap-2 text-start break-words whitespace-normal outline-none keyboard-focused:focus-ring [.text-message+\u0026amp;]:mt-1\" data-message-model-slug=\"gpt-5-5\" dir=\"auto\" data-message-id=\"83c328ce-57fb-4193-be34-0f60ea773aea\" data-message-author-role=\"assistant\" tabindex=\"0\"\u003e\n\u003cdiv class=\"flex w-full flex-col gap-1 empty:hidden\"\u003e\n\u003cdiv class=\"markdown prose dark:prose-invert wrap-break-word w-full light markdown-new-styling\"\u003e\n\u003cul data-is-only-node=\"\" data-is-last-node=\"\" data-end=\"225\" data-start=\"0\"\u003e\n\u003cli data-end=\"39\" data-start=\"0\" data-section-id=\"26xic\"\u003ePrecision-machined \u003cstrong data-end=\"39\" data-start=\"21\"\u003e400cc cylinder\u003c\/strong\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"125\" data-start=\"40\" data-section-id=\"f4na3p\"\u003e\n\u003cstrong data-is-only-node=\"\" data-end=\"76\" data-start=\"42\"\u003eBNR Wiseco 400cc forged piston\u003c\/strong\u003e (includes Wiseco rings, wrist pin, and circlips)\u003c\/li\u003e\n\u003cli data-is-last-node=\"\" data-end=\"225\" data-start=\"126\" data-section-id=\"1yxkwbj\"\u003e\n\u003cstrong data-is-only-node=\"\" data-end=\"157\" data-start=\"128\"\u003e400cc de-bore head gasket\u003c\/strong\u003e designed specifically for the 400cc cylinder and piston combination\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003c\/div\u003e\n\u003cul data-spread=\"false\"\u003e\n\u003cli\u003e\n\u003cstrong style=\"font-size: 0.875rem;\"\u003eNote:\u003c\/strong\u003e\u003cspan style=\"font-size: 0.875rem;\"\u003e A Vortex ECU is required for all 400cc de-bore conversions\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003e\u003cspan\u003eComplete 400cc De-Bore Kit with Vortex ECU\u003c\/span\u003e\u003c\/h3\u003e\n\u003cp class=\"isSelectedEnd\"\u003e\u003cspan\u003eIncludes:\u003c\/span\u003e\u003c\/p\u003e\n\u003cul data-spread=\"false\"\u003e\n\u003cli data-end=\"39\" data-start=\"0\" data-section-id=\"26xic\"\u003ePrecision-machined \u003cstrong data-end=\"39\" data-start=\"21\"\u003e400cc cylinder\u003c\/strong\u003e\u003cspan class=\"PDq2pG_selectionAnchor\" aria-hidden=\"true\"\u003e\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli data-end=\"125\" data-start=\"40\" data-section-id=\"f4na3p\"\u003e\n\u003cstrong data-is-only-node=\"\" data-end=\"76\" data-start=\"42\"\u003eBNR Wiseco 400cc forged piston\u003c\/strong\u003e (includes Wiseco rings, wrist pin, and circlips)\u003c\/li\u003e\n\u003cli data-end=\"157\" data-start=\"126\" data-section-id=\"1udotu5\"\u003e\u003cstrong data-is-only-node=\"\" data-end=\"157\" data-start=\"128\"\u003e400cc de-bore head gasket\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli data-is-last-node=\"\" data-end=\"265\" data-start=\"158\" data-section-id=\"c6snfm\"\u003e\n\u003cstrong data-is-only-node=\"\" data-end=\"178\" data-start=\"160\"\u003eNew Vortex ECU\u003c\/strong\u003e professionally programmed by BNR Motorsports specifically for the 400cc de-bore engine\u003cbr\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp class=\"isSelectedEnd\"\u003e\u003cspan\u003eEach Vortex ECU is custom flashed to match your ATV's engine combination and performance modifications, providing optimized fuel and ignition mapping for maximum power, crisp throttle response, and long-term reliability.\u003c\/span\u003e\u003c\/p\u003e\n\u003ch3\u003e\u003cspan\u003e400cc De-Bore Head Gasket\u003c\/span\u003e\u003c\/h3\u003e\n\u003cp class=\"isSelectedEnd\"\u003e\u003cspan\u003eReplacement head gasket designed specifically for BNR Motorsports 400cc de-bore engine builds.\u003c\/span\u003e\u003c\/p\u003e\n\u003ch3\u003e\u003cspan\u003e400cc De-Bore Piston\u003c\/span\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cspan\u003eReplacement piston for BNR Motorsports 400cc de-bore engine builds.\u003c\/span\u003e\u003c\/p\u003e\n\u003ch3\u003e\u003cspan\u003e\u003cstrong\u003eContact \u003c\/strong\u003e\u003c\/span\u003e\u003c\/h3\u003e\n\u003cp\u003e\u003cspan\u003e\u003cstrong\u003eCall:\u003c\/strong\u003e (330) 549-9799\u003cbr\u003e\u003cstrong\u003eText:\u003c\/strong\u003e (330) 774-1123\u003cbr\u003e\u003cstrong\u003eEmail:\u003c\/strong\u003e \u003ca href=\"mailto:bnrmotorsports@hotmail.com\"\u003ebnrmotorsports@hotmail.com\u003c\/a\u003e\u003c\/span\u003e\u003c\/p\u003e","brand":"BNR Motorsports","offers":[{"title":"Complete 400cc De-Bore Kit","offer_id":48103070597310,"sku":null,"price":1599.99,"currency_code":"USD","in_stock":true},{"title":"Complete 400cc De-Bore Kit with New Vortex ECU","offer_id":48103226081470,"sku":null,"price":2494.99,"currency_code":"USD","in_stock":true},{"title":"400cc De-Bore Head Gasket","offer_id":48103226114238,"sku":null,"price":69.95,"currency_code":"USD","in_stock":true},{"title":"400cc De-Bore Piston","offer_id":48103226147006,"sku":null,"price":329.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0025\/8890\/1446\/files\/IMG-0355.heic?v=1783620807","url":"https:\/\/bnr-motorsports.myshopify.com\/products\/yamaha-yfz450r-debore-400cc","provider":"BNR Motorsports","version":"1.0","type":"link"}