{"product_id":"fmf-gnarly-2-stroke-exhaust-pipe-rieju-mr-300i-025321","title":"FMF - Gnarly - 2026+ Rieju MR 300i","description":"\u003ch1\u003eFMF Gnarly 2 Stroke Exhaust for the 2026+ Rieju MR 300i\u003c\/h1\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"1\" id=\"p-rc_3314aaab9c3bc1bd-163\"\u003e\u003cspan class=\"citation-598 citation-end-598\"\u003eThe FMF Gnarly 2-Stroke Exhaust Pipe (025321) is a heavy-duty, torque-focused expansion chamber engineered specifically for the 2026–2027 Rieju MR 300i fuel-injected enduro platform.\u003csup class=\"superscript\" data-turn-source-index=\"1\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e\u003cspan class=\"\"\u003e Technical woods riding,\u003c\/span\u003e\u003cspan\u003e steep boulder climbs,\u003c\/span\u003e\u003cspan\u003e and hard enduro terrain demand immediate low-RPM throttle response and high impact resistance.\u003c\/span\u003e\u003cspan\u003e Standard factory expansion chambers are constructed from thinner-gauge steel that dents easily against rocks and logs,\u003c\/span\u003e\u003cspan\u003e altering internal exhaust wave tuning and choking engine output.\u003c\/span\u003e \u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c\/p\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"2\" id=\"p-rc_3314aaab9c3bc1bd-164\"\u003e\u003cspan class=\"citation-597 citation-end-597\"\u003eConstructed in the USA from rugged 18-gauge carbon steel and finished in FMF’s signature nickel plating, the 025321 Gnarly pipe is built to withstand direct trail impacts and harsh weather exposure.\u003csup class=\"superscript\" data-turn-source-index=\"2\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e\u003cspan class=\"\"\u003e \u003c\/span\u003e\u003cspan class=\"citation-596 citation-end-596\"\u003eIts internal cone geometry is tuned specifically for Rieju’s 298cc Throttle-Body Fuel Injection (TFI) two-stroke engine, shifting exhaust scavenging efficiency downward to produce stronger bottom-end pull and a thicker midrange power curve.\u003csup class=\"superscript\" data-turn-source-index=\"3\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e\u003cspan class=\"\"\u003e \u003c\/span\u003e\u003cspan class=\"citation-595 citation-end-595\"\u003eThis broader low-end torque delivery reduces clutch abuse in technical singletrack while maintaining clean transitions across the engine's three selectable power maps.\u003csup class=\"superscript\" data-turn-source-index=\"4\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e \u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c\/p\u003e\n\u003ch4 dir=\"ltr\" data-path-to-node=\"3\"\u003eFeatures:\u003c\/h4\u003e\n\u003cul dir=\"ltr\" data-path-to-node=\"4\"\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"4,0,0\" id=\"p-rc_3314aaab9c3bc1bd-165\"\u003e\u003cb data-path-to-node=\"4,0,0\" data-index-in-node=\"0\"\u003eHeavy-Duty 18-Gauge Steel Construction:\u003c\/b\u003e\u003cspan class=\"\"\u003e \u003c\/span\u003e\u003cspan class=\"citation-594 citation-end-594\"\u003eThicker steel wall profile provides superior dent and crush resistance against boulders, logs, and trail debris compared to standard OEM pipes.\u003csup class=\"superscript\" data-turn-source-index=\"5\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e \u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"4,1,0\" id=\"p-rc_3314aaab9c3bc1bd-166\"\u003e\u003cb data-path-to-node=\"4,1,0\" data-index-in-node=\"0\"\u003eLow-to-Midrange Torque Tuning:\u003c\/b\u003e\u003cspan class=\"\"\u003e \u003c\/span\u003e\u003cspan class=\"citation-593 citation-end-593\"\u003eExpansion chamber volume and header taper are engineered to maximize bottom-end tractability and midrange pull for technical enduro riding.\u003csup class=\"superscript\" data-turn-source-index=\"6\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e \u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"4,2,0\"\u003e\u003cb data-path-to-node=\"4,2,0\" data-index-in-node=\"0\"\u003eDurable Nickel-Plated Finish:\u003c\/b\u003e\u003cspan\u003e Corrosion-resistant nickel coating protects the raw steel body from moisture,\u003c\/span\u003e\u003cspan\u003e mud staining,\u003c\/span\u003e\u003cspan\u003e and thermal oxidation.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"4,3,0\" id=\"p-rc_3314aaab9c3bc1bd-167\"\u003e\u003cb data-path-to-node=\"4,3,0\" data-index-in-node=\"0\"\u003eTFI Engine-Specific Geometry:\u003c\/b\u003e\u003cspan class=\"\"\u003e \u003c\/span\u003e\u003cspan class=\"citation-592 citation-end-592\"\u003eDeveloped specifically for the port timing and dual-injector TFI delivery of the 2026+ Rieju 298cc two-stroke powerplant.\u003csup class=\"superscript\" data-turn-source-index=\"7\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e \u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"4,4,0\"\u003e\u003cb data-path-to-node=\"4,4,0\" data-index-in-node=\"0\"\u003eOEM \u0026amp; Aftermarket Silencer Compatibility:\u003c\/b\u003e\u003cspan\u003e Mates cleanly with the factory Rieju OXA silencer as well as FMF Powercore 2.\u003c\/span\u003e\u003cspan\u003e1 and Turbinecore 2.\u003c\/span\u003e\u003cspan\u003e1 silencers.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"4,5,0\"\u003e\u003cb data-path-to-node=\"4,5,0\" data-index-in-node=\"0\"\u003eManifold O-Rings Included:\u003c\/b\u003e\u003cspan\u003e Ships with fresh high-temperature exhaust manifold O-rings for an airtight seal at the cylinder spigot.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"4,6,0\"\u003e\u003cb data-path-to-node=\"4,6,0\" data-index-in-node=\"0\"\u003eMade in the USA:\u003c\/b\u003e\u003cspan\u003e Designed,\u003c\/span\u003e\u003cspan\u003e stamped,\u003c\/span\u003e\u003cspan\u003e and hand-welded at FMF Racing in Rancho Dominguez,\u003c\/span\u003e\u003cspan\u003e California.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4 dir=\"ltr\" data-path-to-node=\"5\"\u003eWhat's in the Box:\u003c\/h4\u003e\n\u003cul dir=\"ltr\" data-path-to-node=\"6\"\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"6,0,0\"\u003e\u003cspan\u003e1x FMF Gnarly Nickel-Plated Expansion Chamber Pipe (Part #025321)\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"6,1,0\"\u003e\u003cspan\u003e2x High-Temperature Exhaust Manifold O-Rings\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"6,2,0\"\u003e\u003cspan\u003e1x FMF Racing Decal Pack\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cspan\u003e\u003cmeta charset=\"utf-8\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003ch4\u003eFitment:\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003ch4\u003e2026–2027 – Rieju MR 300i\u003c\/h4\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4 dir=\"ltr\" data-path-to-node=\"7\"\u003eFitment Notes:\u003c\/h4\u003e\n\u003cul dir=\"ltr\" data-path-to-node=\"8\"\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"8,1,0\"\u003e\u003cb data-path-to-node=\"8,1,0\" data-index-in-node=\"0\"\u003eGeneration Incompatibility Warning:\u003c\/b\u003e\u003cspan\u003e Does \u003c\/span\u003e\u003cb data-path-to-node=\"8,1,0\" data-index-in-node=\"41\"\u003eNOT\u003c\/b\u003e\u003cspan\u003e fit 2020–2025 carbureted Rieju MR 300,\u003c\/span\u003e\u003cspan\u003e MR Pro 300,\u003c\/span\u003e\u003cspan\u003e MR Racing 300,\u003c\/span\u003e\u003cspan\u003e or MR Ranger 300 models (those earlier models utilize the previous-generation carbureted engine and require FMF part number \u003c\/span\u003e\u003ccode data-path-to-node=\"8,1,0\" data-index-in-node=\"235\"\u003e025218\u003c\/code\u003e\u003cspan\u003e).\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"8,2,0\"\u003e\u003cb data-path-to-node=\"8,2,0\" data-index-in-node=\"0\"\u003eSilencer Compatibility:\u003c\/b\u003e\u003cspan\u003e Direct fit with the stock OEM silencer and FMF MR 300i slip-on silencers (such as FMF Powercore 2.\u003c\/span\u003e\u003cspan\u003e1 #025322).\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cmeta charset=\"utf-8\"\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"12\"\u003e\u003cb data-path-to-node=\"12\" data-index-in-node=\"0\"\u003eManifold O-Ring Lubrication \u0026amp; High-Temp RTV Sealing:\u003c\/b\u003e\u003cspan\u003e Install the two supplied exhaust O-rings into the grooves of the FMF header spigot prior to mounting.\u003c\/span\u003e\u003cspan\u003e Apply a thin film of high-temperature copper silicone such as \u003cspan style=\"text-decoration: underline; color: rgb(215, 65, 35);\"\u003e\u003cstrong\u003e\u003ca href=\"https:\/\/www.tmbrmoto.com\/products\/permatex-ultra-copper-maximum-temperature-rtv-silicone-gasket-maker-3oz-81878\" title=\"Shop TMBR MOTO for motorcycle maintenance and repair supplies like Permatex RTV and other sealants. \" style=\"color: rgb(215, 65, 35); text-decoration: underline;\"\u003ePermatex Ultra Copper RTV\u003c\/a\u003e\u003c\/strong\u003e\u003c\/span\u003e over the O-rings and inside the cylinder exhaust flange.\u003c\/span\u003e\u003cspan\u003e The silicone acts as an assembly lubricant so the O-rings do not pinch or roll when sliding the pipe into the cylinder,\u003c\/span\u003e\u003cspan\u003e while curing into a flexible thermal seal that prevents unburned two-stroke oil (\"spooge\") from leaking onto the front engine cases and electronic power valve housing.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"13\"\u003e\u003cb data-path-to-node=\"13\" data-index-in-node=\"0\"\u003eStress-Free Alignment Before Tightening Mounts:\u003c\/b\u003e\u003cspan\u003e Two-stroke expansion chambers undergo extreme thermal expansion cycles and chassis flex.\u003c\/span\u003e\u003cspan\u003e Always hook up the cylinder exhaust springs and slide the mid-pipe into the silencer coupler \u003c\/span\u003e\u003cb data-path-to-node=\"13\" data-index-in-node=\"230\"\u003ebefore\u003c\/b\u003e\u003cspan\u003e tightening the frame mounting bolts.\u003c\/span\u003e\u003cspan\u003e Leave the two chassis mounting bolts loose until the pipe settles naturally into its resting position.\u003c\/span\u003e\u003cspan\u003e If a bracket tab does not align cleanly with the rubber isolator mount,\u003c\/span\u003e\u003cspan\u003e loosen the isolator nut on the frame to adjust its angle rather than prying the pipe into place.\u003c\/span\u003e\u003cspan\u003e Bolting down a pre-stressed pipe transfers harmonic vibration directly to the cylinder flange and increases the risk of cracked mounting tabs during trail impacts.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"14\" id=\"p-rc_3314aaab9c3bc1bd-171\"\u003e\u003cspan class=\"citation-588\"\u003e\u003c\/span\u003e\u003cb data-path-to-node=\"14\" data-index-in-node=\"0\" class=\"\"\u003e\u003cspan class=\"citation-588\"\u003eTFI Fueling \u0026amp; Power Map Pairing:\u003c\/span\u003e\u003c\/b\u003e\u003cspan class=\"citation-588 citation-end-588\"\u003e The 2026+ Rieju MR 300i utilizes a dual-injector Throttle-Body Fuel Injection (TFI) system with three handlebar-selectable maps (Race, Forest, and Wet).\u003csup class=\"superscript\" data-turn-source-index=\"11\"\u003e\u003c!----\u003e\u003c\/sup\u003e\u003c\/span\u003e\u003cspan class=\"\"\u003e The FMF Gnarly 025321 is engineered to operate safely within the factory TFI fuel trims without requiring an aftermarket ECU tuner.\u003c\/span\u003e\u003cspan class=\"\"\u003e For technical rock gardens and slick root climbs,\u003c\/span\u003e\u003cspan class=\"\"\u003e pairing the Gnarly’s increased bottom-end torque with the \u003c\/span\u003e\u003cb data-path-to-node=\"14\" data-index-in-node=\"426\"\u003eForest\u003c\/b\u003e\u003cspan\u003e or \u003c\/span\u003e\u003cb data-path-to-node=\"14\" data-index-in-node=\"436\"\u003eWet\u003c\/b\u003e\u003cspan\u003e maps produces linear,\u003c\/span\u003e\u003cspan class=\"\"\u003e tractable power delivery that minimizes rear-wheel spin.\u003c\/span\u003e \u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c!----\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp dir=\"ltr\" data-path-to-node=\"15\"\u003e\u003cb data-path-to-node=\"15\" data-index-in-node=\"0\"\u003ePost-Wash Nickel Finish Maintenance:\u003c\/b\u003e\u003cspan\u003e While FMF’s nickel plating resists rust far better than bare raw \"works\" pipes,\u003c\/span\u003e\u003cspan\u003e mud baked onto a hot header will eventually stain the finish if left sitting.\u003c\/span\u003e\u003cspan\u003e After pressure-washing the bike,\u003c\/span\u003e\u003cspan\u003e blow standing water off the expansion chamber with compressed air and wipe the pipe down with a light coat of Maxima SC1 or WD-40.\u003c\/span\u003e\u003cspan\u003e When starting the bike after applying protective oil,\u003c\/span\u003e\u003cspan\u003e wipe off excess oil from the header cone first so it does not smoke or burn dark brown spots onto the nickel plating.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003e\n\u003cbr\u003e\u003cmeta charset=\"utf-8\"\u003e\n\u003c\/h4\u003e\n\u003ch4 style=\"text-align: center;\"\u003e\u003cspan\u003e\u003cmeta charset=\"utf-8\"\u003e \u003ca title=\"Shop for FMF exhaust and other parts and accessories at TMBR MOTO. XR650L parts and accessories available at TMBR MOTO\" href=\"https:\/\/www.tmbrmoto.com\/collections\/fmf\"\u003e\u003cimg alt=\"\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0622\/5720\/1317\/files\/FMF_BANNERS_b47a5e51-8c77-4a22-a28b-b8b700a6a0ef.jpg?v=1779296464\"\u003e\u003c\/a\u003e\u003c\/span\u003e\u003c\/h4\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003e\u003cimg height=\"56\" width=\"707\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0622\/5720\/1317\/files\/Made_In_The_USA_24865b83-5069-42c1-b4bc-9e28ee4fe2cb.jpg?v=1719961954\" alt=\"\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003ePart Number:  025321\u003c\/p\u003e","brand":"FMF","offers":[{"title":"Default Title","offer_id":51166118871205,"sku":"FMF-GNARLY-2026-RIEJU-300","price":319.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/5720\/1317\/files\/FMF_Gnarly_2026_Rieju_MR_300i_Exhaust_025321.webp?v=1794514295","url":"https:\/\/www.tmbrmoto.com\/products\/fmf-gnarly-2-stroke-exhaust-pipe-rieju-mr-300i-025321","provider":"TMBR MOTO","version":"1.0","type":"link"}