{"product_id":"honda-trx-xr400r-440cc-big-bore-kit-1","title":"Honda TRX400EX \/ XR400R 440cc Big Bore Kit","description":"\u003c!-- CORE_FITMENT_TABS_START --\u003e\n\u003cstyle\u003e\n#core-product-tabs-10499012755758 .core-tab-radio {\n  position: absolute;\n  opacity: 0;\n  pointer-events: none;\n}\n#core-product-tabs-10499012755758 .core-tab-labels {\n  display: flex;\n  gap: 0;\n  margin: 0 0 16px 0;\n  border-bottom: 1px solid #d8d8d8;\n}\n#core-product-tabs-10499012755758 .core-tab-labels label {\n  display: inline-block;\n  padding: 10px 16px;\n  margin: 0 4px -1px 0;\n  border: 1px solid #d8d8d8;\n  background: #f7f7f7;\n  color: #222;\n  font-weight: 600;\n  cursor: pointer;\n  border-radius: 4px 4px 0 0;\n}\n#core-product-tabs-10499012755758 .core-tab-panel {\n  display: none;\n}\n#core-tab-desc-10499012755758:checked ~ .core-tab-labels label[for=\"core-tab-desc-10499012755758\"],\n#core-tab-fitment-10499012755758:checked ~ .core-tab-labels label[for=\"core-tab-fitment-10499012755758\"] {\n  background: #fff;\n  border-bottom-color: #fff;\n}\n#core-tab-desc-10499012755758:checked ~ .core-tab-panels .core-description-panel {\n  display: block;\n}\n#core-tab-fitment-10499012755758:checked ~ .core-tab-panels .core-fitment-panel {\n  display: block;\n}\n#core-product-tabs-10499012755758 .core-fitment-panel {\n  line-height: 1.5;\n}\n\u003c\/style\u003e\n\n\u003cdiv id=\"core-product-tabs-10499012755758\"\u003e\n  \u003cinput class=\"core-tab-radio\" type=\"radio\" name=\"core-product-tabs-10499012755758\" id=\"core-tab-desc-10499012755758\" checked\u003e\n  \u003cinput class=\"core-tab-radio\" type=\"radio\" name=\"core-product-tabs-10499012755758\" id=\"core-tab-fitment-10499012755758\"\u003e\n\n  \u003cdiv class=\"core-tab-labels\"\u003e\n    \u003clabel for=\"core-tab-desc-10499012755758\"\u003eDescription\u003c\/label\u003e\n    \u003clabel for=\"core-tab-fitment-10499012755758\"\u003eVehicle Fitment\u003c\/label\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv class=\"core-tab-panels\"\u003e\n    \u003cdiv class=\"core-tab-panel core-description-panel\"\u003e\n\u003c!-- CORE_DESCRIPTION_START --\u003e\n\u003ch2 style=\"font-size:22px;line-height:1.3;\"\u003eHonda TRX400EX \/ XR400R 440cc Big Bore Kit - 89mm 10:1 Piston + Complete Gasket Kit (1996-2016)\u003c\/h2\u003e\n\u003cp style=\"color:#333;\"\u003eBreathe New Life Into Your Honda — 440cc of Reliable, Affordable Power. Stop leaving power on the table with a stock 400cc cylinder. This complete 440cc big bore kit from 50 Caliber Racing bolts directly onto all Honda TRX400EX, TRX400X, and XR400R models from 1996–2016. The 89mm cylinder features an improved design with a larger sleeve for longer-lasting performance, paired with a hard anodized 10:1 piston dome for improved compression and throttle response. Everything you need is in the box — no hunting for separate parts. If you can turn a wrench, you can install this kit.\u003c\/p\u003e\n\u003cdiv style=\"display:flex;flex-wrap:wrap;gap:12px;margin:24px 0;\"\u003e\n\u003cdiv style=\"background:#f9f9f9;border-top:3px solid #cc0000;padding:14px;text-align:center;border-radius:6px;flex:1 1 120px;\"\u003e\n\u003cspan style=\"font-size:22px;font-weight:bold;color:#111;\"\u003e440cc\u003c\/span\u003e\u003cdiv style=\"font-size:12px;color:#555;\"\u003eDisplacement\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;border-top:3px solid #cc0000;padding:14px;text-align:center;border-radius:6px;flex:1 1 120px;\"\u003e\n\u003cspan style=\"font-size:22px;font-weight:bold;color:#111;\"\u003e89mm\u003c\/span\u003e\u003cdiv style=\"font-size:12px;color:#555;\"\u003eBore Size\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;border-top:3px solid #cc0000;padding:14px;text-align:center;border-radius:6px;flex:1 1 120px;\"\u003e\n\u003cspan style=\"font-size:22px;font-weight:bold;color:#111;\"\u003e10:1\u003c\/span\u003e\u003cdiv style=\"font-size:12px;color:#555;\"\u003eCompression Ratio\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;border-top:3px solid #cc0000;padding:14px;text-align:center;border-radius:6px;flex:1 1 120px;\"\u003e\n\u003cspan style=\"font-size:22px;font-weight:bold;color:#111;\"\u003eBolt-On\u003c\/span\u003e\u003cdiv style=\"font-size:12px;color:#555;\"\u003eInstall Type\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003chr style=\"border:none;border-top:1px solid #eee;margin:24px 0;\"\u003e\n\u003ch3\u003eWhat’s in the Box (Based on selected options)\u003c\/h3\u003e\n\u003cdiv style=\"display:flex;flex-wrap:wrap;gap:12px;margin:16px 0;\"\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:14px;border-radius:6px;flex:1 1 200px;\"\u003e\n\u003cspan style=\"color:#cc0000;font-weight:bold;\"\u003e✓\u003c\/span\u003e 89mm Cylinder with improved sleeve design\u003cdiv style=\"color:#555;font-size:13px;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:14px;border-radius:6px;flex:1 1 200px;\"\u003e\n\u003cspan style=\"color:#cc0000;font-weight:bold;\"\u003e✓\u003c\/span\u003e 10:1 Piston with hard anodized dome\u003cdiv style=\"color:#555;font-size:13px;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:14px;border-radius:6px;flex:1 1 200px;\"\u003e\n\u003cspan style=\"color:#cc0000;font-weight:bold;\"\u003e✓\u003c\/span\u003e Piston ring kit\u003cdiv style=\"color:#555;font-size:13px;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:14px;border-radius:6px;flex:1 1 200px;\"\u003e\n\u003cspan style=\"color:#cc0000;font-weight:bold;\"\u003e✓\u003c\/span\u003e Complete gasket kit\u003cdiv style=\"color:#555;font-size:13px;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:14px;border-radius:6px;flex:1 1 200px;\"\u003e\n\u003cspan style=\"color:#cc0000;font-weight:bold;\"\u003e✓\u003c\/span\u003e Wrist pin\u003cdiv style=\"color:#555;font-size:13px;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:14px;border-radius:6px;flex:1 1 200px;\"\u003e\n\u003cspan style=\"color:#cc0000;font-weight:bold;\"\u003e✓\u003c\/span\u003e Circlips\u003cdiv style=\"color:#555;font-size:13px;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:14px;border-radius:6px;flex:1 1 200px;\"\u003e\n\u003cspan style=\"color:#cc0000;font-weight:bold;\"\u003e✓\u003c\/span\u003e O-rings\u003cdiv style=\"color:#555;font-size:13px;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"r1-desc-media\" data-r1-media-index=\"1\" style=\"display:block;border-radius:8px;margin:24px 0;overflow:hidden;\"\u003e\u003c\/div\u003e\n\u003chr style=\"border:none;border-top:1px solid #eee;margin:24px 0;\"\u003e\n\u003ch3\u003eWhy Riders Upgrade\u003c\/h3\u003e\n\u003cdiv style=\"border:1px solid #eee;border-radius:8px;overflow:hidden;margin:16px 0;\"\u003e\n\u003cdiv style=\"display:flex;align-items:flex-start;padding:14px;background: #fff;\"\u003e\n\u003cspan style=\"font-size:20px;margin-right:12px;flex-shrink:0;\"\u003e🔧\u003c\/span\u003e\u003cdiv style=\"color:#444;font-size:14px;\"\u003e\n\u003cstrong\u003eTrue Bolt-On Install\u003c\/strong\u003e No machining or modifications required — installs with basic mechanical skills.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"display:flex;align-items:flex-start;padding:14px;background: #fafafa;\"\u003e\n\u003cspan style=\"font-size:20px;margin-right:12px;flex-shrink:0;\"\u003e🚀\u003c\/span\u003e\u003cdiv style=\"color:#444;font-size:14px;\"\u003e\n\u003cstrong\u003eSignificant Displacement Gain\u003c\/strong\u003e Increase your engine from 400cc to 440cc for a 10% displacement increase, translating to more torque across the entire RPM range.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"display:flex;align-items:flex-start;padding:14px;background: #fff;\"\u003e\n\u003cspan style=\"font-size:20px;margin-right:12px;flex-shrink:0;\"\u003e⛽\u003c\/span\u003e\u003cdiv style=\"color:#444;font-size:14px;\"\u003e\n\u003cstrong\u003eAggressive Compression on Pump Gas\u003c\/strong\u003e The 10:1 compression ratio is aggressive enough for noticeable performance gains without requiring high-octane race fuel.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"display:flex;align-items:flex-start;padding:14px;background: #fafafa;\"\u003e\n\u003cspan style=\"font-size:20px;margin-right:12px;flex-shrink:0;\"\u003e💪\u003c\/span\u003e\u003cdiv style=\"color:#444;font-size:14px;\"\u003e\n\u003cstrong\u003eDurable Hard Anodized Piston\u003c\/strong\u003e The hard anodized dome resists heat and wear better than standard pistons, ensuring a longer-lasting, reliable upgrade.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"r1-desc-media\" data-r1-media-index=\"2\" style=\"display:block;border-radius:8px;margin:24px 0;overflow:hidden;\"\u003e\u003c\/div\u003e\n\u003cdiv style=\"border:1.5px solid #e8e8e8;border-radius:12px;overflow:hidden;margin:24px 0;\"\u003e\n\u003cdiv style=\"background:#111;padding:14px 18px;display:flex;align-items:center;gap:10px;\"\u003e\n\u003cspan style=\"display:inline-block;width:10px;height:10px;background:#22c55e;border-radius:50%;flex-shrink:0;\"\u003e\u003c\/span\u003e\u003cspan style=\"color:white;font-weight:bold;font-size:15px;\"\u003eIn Stock \u0026amp; Ready To Ship\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"padding:10px 18px;background:#f9f9f9;border-top:1px solid #eee;\"\u003e\u003cem style=\"color:#555;font-size:12px;\"\u003eAlthough rare, some delays may occur. We’ll keep you updated every step of the way.\u003c\/em\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003chr style=\"border:none;border-top:1px solid #eee;margin:24px 0;\"\u003e\n\u003ch3\u003eBig Bore Kit vs. Stock Options\u003c\/h3\u003e\n\u003cdiv style=\"display:flex;flex-wrap:wrap;gap:16px;margin:16px 0;\"\u003e\n\u003cdiv style=\"background:#111;padding:18px;border-radius:8px;flex:1 1 200px;\"\u003e\n\u003cdiv style=\"color:#aaa;font-size:12px;font-weight:bold;margin-bottom:10px;\"\u003eSTOCK 400CC HONDA\u003c\/div\u003e\n\u003cdiv style=\"color:#ccc;font-size:14px;line-height:1.8;\"\u003e\n\u003cspan style=\"color:#888;\"\u003e✗\u003c\/span\u003e Limited displacement\u003cbr\u003e\u003cspan style=\"color:#888;\"\u003e✗\u003c\/span\u003e Less torque across the RPM range\u003cbr\u003e\u003cspan style=\"color:#888;\"\u003e✗\u003c\/span\u003e Potential for increased wear if pushed hard\u003cbr\u003e\u003cspan style=\"color:#888;\"\u003e✗\u003c\/span\u003e Requires engine rebuild for similar gains\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:18px;border-radius:8px;flex:1 1 200px;\"\u003e\n\u003cdiv style=\"color:#cc0000;font-size:12px;font-weight:bold;margin-bottom:10px;\"\u003e⚡ 50 CALIBER RACING 440CC BIG BORE KIT\u003c\/div\u003e\n\u003cdiv style=\"color:#111;font-size:14px;line-height:1.8;\"\u003e\n\u003cspan style=\"color:green;\"\u003e✓\u003c\/span\u003e \u003cstrong\u003e440cc Displacement\u003c\/strong\u003e\u003cbr\u003e\u003cspan style=\"color:green;\"\u003e✓\u003c\/span\u003e \u003cstrong\u003eIncreased torque \u0026amp; throttle response\u003c\/strong\u003e\u003cbr\u003e\u003cspan style=\"color:green;\"\u003e✓\u003c\/span\u003e \u003cstrong\u003e10:1 Compression on Pump Gas\u003c\/strong\u003e\u003cbr\u003e\u003cspan style=\"color:green;\"\u003e✓\u003c\/span\u003e \u003cstrong\u003eHard anodized piston for durability\u003c\/strong\u003e\u003cbr\u003e\u003cspan style=\"color:green;\"\u003e✓\u003c\/span\u003e \u003cstrong\u003eBolt-on installation\u003c\/strong\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003ch3\u003eCommon Questions\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is a big bore kit and how does it work?\u003c\/strong\u003e\u003cspan style=\"color:#444;\"\u003eA big bore kit increases your engine's displacement by using a larger cylinder and piston. This allows for more air and fuel to enter the combustion chamber, resulting in more power and torque.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDo I need to machine my engine to install this kit?\u003c\/strong\u003e\u003cspan style=\"color:#444;\"\u003eNo, this kit is designed as a direct bolt-on upgrade and requires no machining. It installs using basic mechanical skills.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWill this kit work with my specific Honda model and year?\u003c\/strong\u003e\u003cspan style=\"color:#444;\"\u003eThis kit is compatible with all Honda TRX400EX, TRX400X, and XR400R models from 1996 to 2016.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use regular pump gas with this kit?\u003c\/strong\u003e\u003cspan style=\"color:#444;\"\u003eYes, the 10:1 compression ratio is optimized to run on standard pump gas without detonation.\u003c\/span\u003e\u003c\/p\u003e\n\u003cdiv style=\"display:flex;flex-wrap:wrap;gap:12px;margin:24px 0;\"\u003e\n\u003cdiv class=\"r1-desc-media\" data-r1-media-index=\"3\" style=\"flex:1 1 200px;border-radius:8px;background:#f9f9f9;height:260px;overflow:hidden;\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"r1-desc-media\" data-r1-media-index=\"4\" style=\"flex:1 1 200px;border-radius:8px;background:#f9f9f9;height:260px;overflow:hidden;\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background:#f9f9f9;padding:20px;border-radius:8px;margin:24px 0;\"\u003e\u003cdiv style=\"display:flex;flex-wrap:wrap;gap:12px;text-align:center;justify-content:center;\"\u003e\n\u003cdiv style=\"flex:1 1 80px;\"\u003e\n\u003cspan style=\"font-size:22px;\"\u003e🔧\u003c\/span\u003e\u003cdiv style=\"font-weight:bold;color:#111;font-size:13px;\"\u003eExpert Support\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"flex:1 1 80px;\"\u003e\n\u003cspan style=\"font-size:22px;\"\u003e⭐\u003c\/span\u003e\u003cdiv style=\"font-weight:bold;color:#111;font-size:13px;\"\u003eCustomer Favorite\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"flex:1 1 80px;\"\u003e\n\u003cspan style=\"font-size:22px;\"\u003e📦\u003c\/span\u003e\u003cdiv style=\"font-weight:bold;color:#111;font-size:13px;\"\u003eTracked Shipping\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"flex:1 1 80px;\"\u003e\n\u003cspan style=\"font-size:22px;\"\u003e🛠️\u003c\/span\u003e\u003cdiv style=\"font-weight:bold;color:#111;font-size:13px;\"\u003eQuality Guaranteed\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003ch3\u003eWhat Riders Are Saying\u003c\/h3\u003e\n\u003cblockquote style=\"border-left:4px solid #cc0000;padding-left:15px;margin:20px 0;font-style:italic;color:#555;\"\u003eInstalled this on my TRX400EX in an afternoon. The difference in throttle response is immediately noticeable. Kit had everything I needed and the instructions were clear.\u003cbr\u003e\u003cstrong style=\"color:#111;\"\u003e— John D., California\u003c\/strong\u003e\n\u003c\/blockquote\u003e\n\u003cblockquote style=\"border-left:4px solid #cc0000;padding-left:15px;margin:20px 0;font-style:italic;color:#555;\"\u003eMy XR400R had a tired top end. This kit brought it back to life and then some. Bolt-on as advertised — no machining, no surprises.\u003cbr\u003e\u003cstrong style=\"color:#111;\"\u003e— Mark T., Texas\u003c\/strong\u003e\n\u003c\/blockquote\u003e\n\u003cdiv style=\"background:#111;padding:25px;text-align:center;margin:30px 0;border-radius:10px;\"\u003e\n\u003ch2 style=\"color:white;margin:0 0 8px 0;font-size:20px;\"\u003eReady to Unlock More Power?\u003c\/h2\u003e\n\u003cp style=\"color:#bbb;margin:0;font-size:15px;\"\u003eIn Stock Now - Join thousands of Honda owners who trust R1 Industries for reliable, affordable performance upgrades.\u003c\/p\u003e\n\u003cp style=\"color:#777;font-size:13px;margin:10px 0 0 0;\"\u003eStop riding a tired 400. 440cc bolt-on kit, complete with everything — more power, same reliability.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c!-- CORE_DESCRIPTION_END --\u003e\n    \u003c\/div\u003e\n    \u003cdiv class=\"core-tab-panel core-fitment-panel\"\u003e\n      \u003ch3\u003eVehicle Fitment\u003c\/h3\u003e\nHonda TRX400EX — 1996-2016\u003cbr\u003e\nHonda TRX400X — 1996-2016\u003cbr\u003e\nHonda XR400R — 1996-2003\u003cbr\u003e\n    \u003c\/div\u003e\n  \u003c\/div\u003e\n\u003c\/div\u003e\n\u003c!-- CORE_FITMENT_TABS_END --\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":51961831620910,"sku":"4449A13","price":69.99,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0265\/4076\/9342\/files\/3154_feaa401d-78e5-4205-b8c7-0141823556d0.jpg?v=1776204395","url":"https:\/\/r1industriesoffroad.com\/es\/products\/honda-trx-xr400r-440cc-big-bore-kit-1","provider":"R1 Industries","version":"1.0","type":"link"}