{"product_id":"537338701-trimmer-head-bump-knob-4pack","title":"537338701 Trimmer Head Bump Knob - Fits Husqvarna T25 Heads (124L, 125L, 125LDx - 4 Pack","description":"\u003ch2\u003e537338701 Trimmer Head Bump Knob\u003c\/h2\u003e\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh-Density Wear Polymer:\u003c\/strong\u003e Engineered from specialized, abrasion-resistant plastic to withstand the high-velocity friction of tapping against concrete, asphalt, and rocky soil.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInternal Spring-Loaded Interface:\u003c\/strong\u003e Designed with precision-molded internal slots to securely house the trimmer head spring, ensuring a consistent and responsive \"snap-back\" after every tap.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBalanced Impact Surface:\u003c\/strong\u003e Features a reinforced, flat-bottom design that ensures even wear and prevents the trimmer head from wobbling at high RPMs.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh-Visibility Blue:\u003c\/strong\u003e The signature factory-match color allows for easy inspection of wear levels and ensures the knob is easy to locate during field maintenance.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTool-Free Installation:\u003c\/strong\u003e A direct-fit replacement that snaps into the existing T25 housing by hand, allowing for rapid repairs without the need for additional tools.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eReplaces \/ Cross-Reference Part Numbers\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e537338701\u003c\/li\u003e\n\u003cli\u003e537 33 87-01\u003cbr\u003e\n\u003c\/li\u003e\n\u003cli\u003e966674401 (Associated Head)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eCompatibility \u0026amp; Fitment\u003c\/h3\u003e\n\u003cp\u003eThis bump knob is the standard replacement part for the Husqvarna T25 (Tap Advance) series trimmer heads. Key compatible models include:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHusqvarna 120 Series:\u003c\/strong\u003e 124L, 125L, 125LDx, 128L, 128LD, 128LDx, 128R, 128RJ.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHusqvarna 200 Series:\u003c\/strong\u003e 223L, 223R, 26LC.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHusqvarna 300 Series:\u003c\/strong\u003e 32LC, 322L, 323L, 325L.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNote:\u003c\/strong\u003e This part is specifically for the \u003cstrong\u003eT25\u003c\/strong\u003e head. If you have the larger T35 or T45 head, you will require a different part number.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eWhen to Replace\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eGround-Through Surface:\u003c\/strong\u003e The bottom of the blue knob has worn down so thin that the internal spring is visible or has already fallen out.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBroken Retaining Tabs:\u003c\/strong\u003e The plastic clips that hold the knob inside the trimmer head housing have snapped, causing the knob to fly off during operation.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSeized Mechanism:\u003c\/strong\u003e Dirt and dried sap have fused the knob to the internal spool, preventing it from being \"tapped\" to release new line.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRounded Edges:\u003c\/strong\u003e Significant wear has rounded the edges of the knob to the point where it no longer triggers the internal indexing mechanism reliably.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCracked Housing:\u003c\/strong\u003e Visible stress fractures in the blue plastic which can cause the knob to shatter at high RPMs.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eInstallation Tips\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eClean the Housing:\u003c\/strong\u003e Before installing the new knob, use a stiff brush to remove all dried grass, mud, and debris from inside the trimmer head and around the spring.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCheck the Spring:\u003c\/strong\u003e Inspect the internal metal spring for rust or loss of tension. If the spring is weak, the new knob will not retract properly, causing the head to dump all the line at once.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTab Alignment:\u003c\/strong\u003e Align the retaining tabs of the new knob with the slots in the T25 housing. Press down firmly until you hear a distinct \"click\" on both sides.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManual Feed Test:\u003c\/strong\u003e Once installed, press the knob in by hand and pull the line to ensure the internal spool is releasing the line correctly before starting the engine.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAvoid Dragging:\u003c\/strong\u003e To prolong the life of your new knob, avoid letting the trimmer head \"ride\" on the ground while trimming; only make contact with the surface when you need to advance the line.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"BlueStarsParts","offers":[{"title":"Default Title","offer_id":45371209744573,"sku":"AZ00484947","price":11.7,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/2576\/7548\/files\/AZ00484947_1_d0b1cff7-929c-4cab-ab8f-892e5063feac.jpg?v=1762246296","url":"https:\/\/bluestarsparts.com\/products\/537338701-trimmer-head-bump-knob-4pack","provider":"BlueStars Parts","version":"1.0","type":"link"}