{"product_id":"honda-trx-xr400r-440cc-big-bore-kit-1","title":"Honda TRX400EX \/ XR400R 440cc Big Bore Kit - 89mm 10:1 Piston + Complete Gasket Kit (1996-2016)","description":"\u003cdiv style=\"background: #cc0000; color: white; padding: 20px; margin: 0 0 20px 0; text-align: center; font-size: 20px; font-weight: bold; border-radius: 5px;\"\u003e⚡ COMPLETE KIT | 89MM 10:1 PISTON | BOLT-ON POWER UPGRADE ⚡\u003c\/div\u003e\u003ch2\u003eBreathe New Life Into Your Honda — 440cc of Reliable, Affordable Power\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eStop leaving power on the table with a stock 400cc cylinder.\u003c\/strong\u003e 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\u003cdiv style=\"background: #f4f4f4; padding: 15px; margin: 20px 0; border-left: 4px solid #cc0000;\"\u003e\n\u003cstrong\u003e⚡ IN STOCK\u003c\/strong\u003e | \u003cstrong\u003eShips Fast\u003c\/strong\u003e\n\u003c\/div\u003e\u003ch3\u003eWhy Honda Owners Choose This Big Bore Kit\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eTrue Bolt-On Install\u003c\/strong\u003e — No machining or modifications required — installs with basic mechanical skills\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e89mm 10:1 Piston\u003c\/strong\u003e — Hard anodized dome for improved compression and heat resistance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eImproved Cylinder Design\u003c\/strong\u003e — Larger sleeve for longer-lasting performance vs. stock\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete Kit\u003c\/strong\u003e — Cylinder, piston, rings, gaskets, wrist pin, circlips, and O-rings all included\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFits 20 Years of Honda Models\u003c\/strong\u003e — Compatible with TRX400EX, TRX400X, and XR400R from 1996–2016\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAffordable Power\u003c\/strong\u003e — Significant displacement gain at a fraction of the cost of a new engine\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003ePerfect For\u003c\/h3\u003e\u003cp\u003e🏍️ Trail and recreational riding  |  🏜️ Desert and dune riding  |  🏎️ Track and racing builds  |  🔧 ATV restoration and refresh  |  💪 Performance upgrades on a budget\u003c\/p\u003e\u003ch3\u003eComplete Kit Includes\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e✓ 89mm cylinder with improved sleeve design\u003c\/li\u003e\n\u003cli\u003e✓ 10:1 piston with hard anodized dome\u003c\/li\u003e\n\u003cli\u003e✓ Piston ring kit\u003c\/li\u003e\n\u003cli\u003e✓ Complete gasket kit\u003c\/li\u003e\n\u003cli\u003e✓ Wrist pin\u003c\/li\u003e\n\u003cli\u003e✓ Circlips\u003c\/li\u003e\n\u003cli\u003e✓ O-rings\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eDisplacement\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e440cc\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eBore\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e89mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eCompression Ratio\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e10:1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003ePiston Finish\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003eHard anodized dome\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eInstall Type\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003eBolt-on, no machining required\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eKit Contents\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003eCylinder, piston, rings, gaskets, wrist pin, circlips, O-rings\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\u003ch3\u003eVehicle Fitment\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003eHonda TRX400EX (1996–2016)\u003c\/li\u003e\n\u003cli\u003eHonda TRX400X (1996–2016)\u003c\/li\u003e\n\u003cli\u003eHonda XR400R (1996–2003)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eWhy a Big Bore Kit Is the Best Bang-for-Buck Honda Power Upgrade\u003c\/h3\u003e\u003cp\u003eA big bore kit is the most cost-effective way to add displacement to a four-stroke engine. Going from 400cc to 440cc is a 10% displacement increase — which translates directly to more torque across the entire RPM range, not just at peak power. You feel it in throttle response off the bottom, in mid-range pull on climbs, and in top-end confidence at speed. The 10:1 compression ratio on this piston is aggressive enough to wake up the engine without requiring race fuel — it runs on pump gas. The hard anodized dome resists heat and wear better than a standard piston, which means this kit lasts. If your Honda is tired or you just want more, this is where to start.\u003c\/p\u003e\u003cblockquote style=\"border-left: 4px solid #cc0000; padding-left: 15px; margin: 20px 0; font-style: italic;\"\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. — Verified Buyer\u003c\/blockquote\u003e\u003cblockquote style=\"border-left: 4px solid #cc0000; padding-left: 15px; margin: 20px 0; font-style: italic;\"\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. — Verified Buyer\u003c\/blockquote\u003e\u003ch3\u003e100% Risk-Free With R1 Protect\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e30-Day Returns\u003c\/strong\u003e — Not the right fit? Send it back, no hassle\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast Shipping\u003c\/strong\u003e — In stock and ready to ship\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eExpert Support\u003c\/strong\u003e — 801-899-2520 | Real UTV techs, not a call center\u003c\/li\u003e\n\u003c\/ul\u003e\u003cdiv style=\"background: #cc0000; color: white; padding: 20px; margin: 20px 0; text-align: center; border-radius: 5px;\"\u003e\n\u003ch3 style=\"color: white; margin-top: 0;\"\u003e⚡ Ready to Unlock More Power?\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eIn Stock Now\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eJoin thousands of Honda owners who trust R1 Industries for reliable, affordable performance upgrades.\u003c\/p\u003e\n\u003c\/div\u003e\u003cp style=\"text-align: center; color: #666; font-size: 12px;\"\u003e\u003cem\u003eStop riding a tired 400. 440cc bolt-on kit, complete with everything — more power, same reliability.\u003c\/em\u003e\u003c\/p\u003e","brand":"50 Caliber Racing","offers":[{"title":"Default Title","offer_id":51961831620910,"sku":"4449A13","price":69.99,"currency_code":"USD","in_stock":true}],"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\/products\/honda-trx-xr400r-440cc-big-bore-kit-1","provider":"R1 Industries","version":"1.0","type":"link"}