{"product_id":"royal-enfield-550025-nut-main-shaft-oem","title":"Royal Enfield 550025 – Nut-Main Shaft (M12 X 1.25 Nylock) OEM for 500 \u0026 350 UCE \/ Classic \u0026 Bullet Models","description":"\u003cp data-start=\"1501\" data-end=\"2049\"\u003eEnsure secure fastening of your crank\/drive main shaft with the genuine Royal Enfield \u003cstrong data-start=\"1630\" data-end=\"1655\"\u003e550025 Nut-Main Shaft\u003c\/strong\u003e. This OEM nut is engineered to the exact factory thread spec (M12 x 1.25 Nylock “P” Type) to retain the main shaft securely under dynamic engine loads. Used across many Royal Enfield models — including \u003cstrong data-start=\"1858\" data-end=\"1873\"\u003eClassic 500\u003c\/strong\u003e, \u003cstrong data-start=\"1875\" data-end=\"1889\"\u003eBullet 500\u003c\/strong\u003e, \u003cstrong data-start=\"1891\" data-end=\"1906\"\u003eClassic 350\u003c\/strong\u003e, \u003cstrong data-start=\"1908\" data-end=\"1922\"\u003eBullet 350\u003c\/strong\u003e, \u003cstrong data-start=\"1924\" data-end=\"1946\"\u003eContinental GT 535\u003c\/strong\u003e, and other UCE variants — it’s the same nut fitted at the factory for crankcase\/main shaft assembly.\u003c\/p\u003e\n\u003cp data-start=\"2051\" data-end=\"2490\"\u003eIf your existing nut is worn, the Nylock collar is damaged, or the bolt loosens under vibration, replacing it with 550025 restores the correct clamping force, preventing crank play, oil leaks, or shaft looseness. Because the nut is vital to engine safety, always double-check the old nut’s size, thread pitch, and feature (lock-type). This genuine part ensures factory fit, durability, and compatibility with stock shafts and crankcases.\u003c\/p\u003e\n\u003chr data-start=\"2492\" data-end=\"2495\"\u003e\n\u003cp data-start=\"2497\" data-end=\"2516\"\u003e\u003cstrong data-start=\"2497\" data-end=\"2514\"\u003eKey Features:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-start=\"2517\" data-end=\"3105\"\u003e\n\u003cli data-start=\"2517\" data-end=\"2628\"\u003e\n\u003cp data-start=\"2519\" data-end=\"2628\"\u003eGenuine Royal Enfield OEM \u003cstrong data-start=\"2545\" data-end=\"2570\"\u003e550025 Nut-Main Shaft\u003c\/strong\u003e per factory spec. \u003cspan class=\"\" data-state=\"closed\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"2629\" data-end=\"2756\"\u003e\n\u003cp data-start=\"2631\" data-end=\"2756\"\u003eM12 x 1.25 thread, Nylock-type lock-nut “P” type (self-locking) for secure retention. \u003cspan class=\"\" data-state=\"closed\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"2757\" data-end=\"2891\"\u003e\n\u003cp data-start=\"2759\" data-end=\"2891\"\u003eFits many UCE models: Classic 500, Bullet 500, Classic 350, Bullet 350, Continental GT, etc. \u003cspan class=\"\" data-state=\"closed\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"2892\" data-end=\"2947\"\u003e\n\u003cp data-start=\"2894\" data-end=\"2947\"\u003eHardened steel finish to resist vibration loosening\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"2948\" data-end=\"3032\"\u003e\n\u003cp data-start=\"2950\" data-end=\"3032\"\u003eLow profile — designed for precise fit with stock main shaft washer \u0026amp; components\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"3033\" data-end=\"3105\"\u003e\n\u003cp data-start=\"3035\" data-end=\"3105\"\u003eCritical for maintaining crankcase integrity \u0026amp; smooth power transfer\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr data-start=\"3107\" data-end=\"3110\"\u003e\n\u003cp data-start=\"3112\" data-end=\"3136\"\u003e\u003cstrong data-start=\"3112\" data-end=\"3136\"\u003eCompatibility Table:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cdiv class=\"_tableContainer_1rjym_1\"\u003e\n\u003cdiv class=\"group _tableWrapper_1rjym_13 flex w-fit flex-col-reverse\" tabindex=\"-1\"\u003e\n\u003ctable data-start=\"3138\" data-end=\"3607\" class=\"w-fit min-w-(--thread-content-width)\"\u003e\n\u003cthead data-start=\"3138\" data-end=\"3202\"\u003e\n\u003ctr data-start=\"3138\" data-end=\"3202\"\u003e\n\u003cth data-start=\"3138\" data-end=\"3146\" data-col-size=\"sm\"\u003eModel\u003c\/th\u003e\n\u003cth data-start=\"3146\" data-end=\"3166\" data-col-size=\"sm\"\u003eEngine \/ Platform\u003c\/th\u003e\n\u003cth data-start=\"3166\" data-end=\"3193\" data-col-size=\"sm\"\u003eEmission \/ Region \/ Spec\u003c\/th\u003e\n\u003cth data-start=\"3193\" data-end=\"3202\" data-col-size=\"md\"\u003eNotes\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody data-start=\"3221\" data-end=\"3607\"\u003e\n\u003ctr data-start=\"3221\" data-end=\"3326\"\u003e\n\u003ctd data-start=\"3221\" data-end=\"3241\" data-col-size=\"sm\"\u003eClassic 500 (UCE)\u003c\/td\u003e\n\u003ctd data-start=\"3241\" data-end=\"3283\" data-col-size=\"sm\"\u003e499 cc UCE \/ Gear-\/Crankcase main shaft\u003c\/td\u003e\n\u003ctd data-start=\"3283\" data-end=\"3313\" data-col-size=\"sm\"\u003eUK \/ Export \/ Euro III \u0026amp; IV\u003c\/td\u003e\n\u003ctd data-start=\"3313\" data-end=\"3326\" data-col-size=\"md\"\u003eConfirmed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr data-start=\"3327\" data-end=\"3378\"\u003e\n\u003ctd data-start=\"3327\" data-end=\"3344\" data-col-size=\"sm\"\u003eBullet 500 UCE\u003c\/td\u003e\n\u003ctd data-start=\"3344\" data-end=\"3353\" data-col-size=\"sm\"\u003e499 cc\u003c\/td\u003e\n\u003ctd data-start=\"3353\" data-end=\"3365\" data-col-size=\"sm\"\u003eSame spec\u003c\/td\u003e\n\u003ctd data-start=\"3365\" data-end=\"3378\" data-col-size=\"md\"\u003eConfirmed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr data-start=\"3379\" data-end=\"3436\"\u003e\n\u003ctd data-start=\"3379\" data-end=\"3400\" data-col-size=\"sm\"\u003eContinental GT 535\u003c\/td\u003e\n\u003ctd data-start=\"3400\" data-end=\"3409\" data-col-size=\"sm\"\u003e535 cc\u003c\/td\u003e\n\u003ctd data-start=\"3409\" data-end=\"3423\" data-col-size=\"sm\"\u003eExport \/ UK\u003c\/td\u003e\n\u003ctd data-start=\"3423\" data-end=\"3436\" data-col-size=\"md\"\u003eConfirmed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr data-start=\"3437\" data-end=\"3551\"\u003e\n\u003ctd data-start=\"3437\" data-end=\"3455\" data-col-size=\"sm\"\u003eClassic 350 UCE\u003c\/td\u003e\n\u003ctd data-start=\"3455\" data-end=\"3464\" data-col-size=\"sm\"\u003e349 cc\u003c\/td\u003e\n\u003ctd data-start=\"3464\" data-end=\"3485\" data-col-size=\"sm\"\u003eBS4 \/ BS6 \/ Export\u003c\/td\u003e\n\u003ctd data-start=\"3485\" data-end=\"3551\" data-col-size=\"md\"\u003eLikely fit (same main shaft threads), verify existing nut type\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr data-start=\"3552\" data-end=\"3607\"\u003e\n\u003ctd data-start=\"3552\" data-end=\"3569\" data-col-size=\"sm\"\u003eBullet 350 UCE\u003c\/td\u003e\n\u003ctd data-start=\"3569\" data-end=\"3578\" data-col-size=\"sm\"\u003e349 cc\u003c\/td\u003e\n\u003ctd data-start=\"3578\" data-end=\"3585\" data-col-size=\"sm\"\u003eSame\u003c\/td\u003e\n\u003ctd data-start=\"3585\" data-end=\"3607\" data-col-size=\"md\"\u003eCheck Part Number\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003chr data-start=\"3609\" data-end=\"3612\"\u003e\n\u003cp data-start=\"3614\" data-end=\"3629\"\u003e\u003cstrong data-start=\"3614\" data-end=\"3627\"\u003eVariants:\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul data-start=\"3630\" data-end=\"3812\"\u003e\n\u003cli data-start=\"3630\" data-end=\"3680\"\u003e\n\u003cp data-start=\"3632\" data-end=\"3680\"\u003e550025 (standard) — M12 × 1.25 Nylock “P” Type\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"3681\" data-end=\"3784\"\u003e\n\u003cp data-start=\"3683\" data-end=\"3784\"\u003eSometimes called 550025\/A in parts list when suffix is given. \u003cspan class=\"\" data-state=\"closed\"\u003e\u003cspan class=\"ms-1 inline-flex max-w-full items-center relative top-[-0.094rem] animate-[show_150ms_ease-in]\" data-testid=\"webpage-citation-pill\"\u003e\u003c\/span\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"3785\" data-end=\"3812\"\u003e\n\u003cp data-start=\"3787\" data-end=\"3812\"\u003eSupplied as single unit\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"3785\" data-end=\"3812\"\u003eCheck Part Number Before Purchase\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr data-start=\"3814\" data-end=\"3817\"\u003e\n\u003cp data-start=\"3819\" data-end=\"3830\"\u003e\u003cstrong data-start=\"3819\" data-end=\"3828\"\u003eFAQs:\u003c\/strong\u003e\u003c\/p\u003e\n\u003col data-start=\"3832\" data-end=\"4966\"\u003e\n\u003cli data-start=\"3832\" data-end=\"4068\"\u003e\n\u003cp data-start=\"3835\" data-end=\"4068\"\u003e\u003cstrong data-start=\"3835\" data-end=\"3899\"\u003eHow do I ensure 550025 is the correct nut for my main shaft?\u003c\/strong\u003e\u003cbr data-start=\"3899\" data-end=\"3902\"\u003e→ Remove the old nut and check if it’s stamped “550025”, note thread pitch (M12 × 1.25), and if it’s a nylon locking style (“Nylock”). Match these before ordering.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"4070\" data-end=\"4293\"\u003e\n\u003cp data-start=\"4073\" data-end=\"4293\"\u003e\u003cstrong data-start=\"4073\" data-end=\"4135\"\u003eWhat happens if I use a generic nut instead of OEM 550025?\u003c\/strong\u003e\u003cbr data-start=\"4135\" data-end=\"4138\"\u003e→ Risks include loosening under vibration, oil leaks, main shaft play, or damage to crankcase threads. OEM ensures correct locking and material quality.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"4295\" data-end=\"4538\"\u003e\n\u003cp data-start=\"4298\" data-end=\"4538\"\u003e\u003cstrong data-start=\"4298\" data-end=\"4338\"\u003eIs 550025 used on 350 cc models too?\u003c\/strong\u003e\u003cbr data-start=\"4338\" data-end=\"4341\"\u003e→ Yes, many listings (The Spares Company etc.) show fitment across Classic\/Bullet 350 and 500 UCE models. But verify your existing nut for thread and style. \u003cspan class=\"\" data-state=\"closed\"\u003e\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"4540\" data-end=\"4772\"\u003e\n\u003cp data-start=\"4543\" data-end=\"4772\"\u003e\u003cstrong data-start=\"4543\" data-end=\"4600\"\u003eDo I need any extra washers or parts while replacing?\u003c\/strong\u003e\u003cbr data-start=\"4600\" data-end=\"4603\"\u003e→ Usually the existing washer(s) under the nut, main shaft and crankcase are reused if undamaged. But inspect for wear; washers that are distorted should be replaced.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"4774\" data-end=\"4966\"\u003e\n\u003cp data-start=\"4777\" data-end=\"4966\"\u003e\u003cstrong data-start=\"4777\" data-end=\"4821\"\u003eWhat torque spec is needed for this nut?\u003c\/strong\u003e\u003cbr data-start=\"4821\" data-end=\"4824\"\u003e→ Use the service manual for your model to get correct torque — over-tightening may damage threads, under-tightening may cause loosening.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ol\u003e","brand":"UNDER THE HOOD","offers":[{"title":"Default Title","offer_id":50439663780135,"sku":null,"price":15.0,"currency_code":"INR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0878\/7447\/0183\/files\/550025_main_shaft_nut_for_Classic_500_RE.png?v=1758372907","url":"https:\/\/underthehood.co.in\/products\/royal-enfield-550025-nut-main-shaft-oem","provider":"UNDER THE HOOD","version":"1.0","type":"link"}