{"product_id":"castair-replacement-motor-pulley-1-3-8-fixed-bore-shaft-7-5-od-2b-grooves","title":"Castair Replacement Motor Pulley 1 3\/8\" Fixed Bore Shaft 7.5\" OD. 2B Grooves","description":"\u003cp\u003eThe Castair P2B725-11\/8 is a 2-groove (2B) replacement motor pulley with a 1-3\/8\" fixed bore and 7.5\" outer diameter, for use in Cast Air belt-drive air compressor systems. Note: the product name in the listing references both \"1 3\/8\" bore and \"7.5\" OD\" — this description reflects both dimensions as listed. The 7.5\" OD is a larger motor pulley than the 6.25\" and 6.75\" units in the Cast Air lineup, which means it drives the pump faster for a given motor RPM, increasing CFM output where the pump design supports it.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eNote: Cast Air did not provide a dedicated manufacturer product page for this pulley.\u003c\/strong\u003e Specifications are drawn from the product listing. Confirm fitment with your specific compressor model before ordering — call us if you need help.\u003c\/p\u003e\n\n\u003ch2\u003eWhat Makes This Pulley Different From the Smaller OD Options\u003c\/h2\u003e\n\u003cp\u003eThe key difference between motor pulleys in the Cast Air lineup is the outer diameter. The OD sets the belt drive ratio relative to the pump flywheel. A larger motor pulley OD increases the ratio, spinning the pump faster. A 7.5\" motor pulley paired with a standard 14\" pump flywheel gives a drive ratio of approximately 1.87:1 — so a 1,750 RPM motor drives the pump at roughly 935 RPM. This is toward the upper end of the normal range for single-stage Cast Air pumps and is appropriate for applications where higher CFM output is needed from the same motor.\u003c\/p\u003e\n\n\u003ch3\u003ePulley Specification Details\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eGroove Profile:\u003c\/strong\u003e 2B (two B-section V-belt grooves)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBore Type:\u003c\/strong\u003e Fixed bore — 1-3\/8\" (1.375\") shaft diameter\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOuter Diameter (OD):\u003c\/strong\u003e 7.5\"\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Motor-side pulley for belt-drive air compressors\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e Cast Air belt-drive compressor systems with 1-3\/8\" motor shafts and B-section belts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P2B725-11\/8\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eFixed Bore vs. Taper-Lock — Which Do You Have?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFixed bore (this pulley):\u003c\/strong\u003e Machined for a specific shaft diameter. Mounts with keyway and set screw directly on the motor shaft. Correct for direct replacement when your original was also a fixed bore 1-3\/8\" unit.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTaper-lock (SK\/SD):\u003c\/strong\u003e Uses a removable bushing that adapts to multiple shaft sizes. A different part entirely — not interchangeable with fixed bore without modification.\u003c\/li\u003e\n\u003cli\u003eIf your original pulley was fixed bore and measured 7.5\" OD with a 1-3\/8\" bore, the P2B725-11\/8 is the direct replacement.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen Does a Shop Need the 7.5\" OD Pulley?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eOriginal motor pulley measured 7.5\" OD with 1-3\/8\" fixed bore and is now worn or damaged\u003c\/li\u003e\n\u003cli\u003eApplication requires higher pump RPM than the 6.25\" or 6.75\" pulleys provide\u003c\/li\u003e\n\u003cli\u003eRebuilding a Cast Air compressor that originally shipped with a 7.5\" motor pulley\u003c\/li\u003e\n\u003cli\u003ePump CFM output is below spec and tachometer confirms the pump RPM is too low — a larger motor pulley corrects this\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e2B Fixed-Bore 1-3\/8\" Motor Pulley Size Comparison\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B625-13\/8 — 6.25\" OD — $68.34\u003c\/strong\u003e — lowest pump RPM in the fixed-bore series\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B675-13\/8 — 6.75\" OD — $71.23\u003c\/strong\u003e — mid-range OD for standard single-stage applications\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B725-11\/8 — 7.5\" OD — $84.70\u003c\/strong\u003e (this unit) — larger OD, higher pump RPM, higher CFM potential\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B80-13\/8 — 8.0\" OD — $88.55\u003c\/strong\u003e — even larger, for applications requiring maximum pump speed ratio\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B875-13\/8 — 8.75\" OD — $103.95\u003c\/strong\u003e — largest fixed-bore option\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P2B725-11\/8\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Cast Air (Castair)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGroove Type:\u003c\/strong\u003e 2B (two B-section V-belt grooves)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBore:\u003c\/strong\u003e Fixed, 1-3\/8\" (1.375\")\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOuter Diameter:\u003c\/strong\u003e 7.5\"\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBore Style:\u003c\/strong\u003e Fixed (keyway and set screw mount)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBelt Section:\u003c\/strong\u003e B-section (two matched belts)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $84.70\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer Data:\u003c\/strong\u003e Product page not available — specifications from product listing data\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat Is Included\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1x Castair P2B725-11\/8 motor pulley\u003c\/li\u003e\n\u003cli\u003eSet screw(s) for shaft retention\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eB-section matched belts sold separately. Measure your drive center distance to determine the correct belt length.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h2\u003e\n\u003cp\u003eSince 2016, we have stocked Cast Air replacement parts across the full pulley lineup. If you are not certain whether the 7.5\" OD is the correct size for your compressor, call us before ordering. We can help you identify the right pulley based on your compressor model and original specifications. Free shipping, free tech support, and full manufacturer warranty on every part we sell.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCast Air specialist\u003c\/strong\u003e since 2016\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on all orders\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree tech support\u003c\/strong\u003e — we confirm fitment before you order\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHonest guidance\u003c\/strong\u003e on which OD is correct for your application\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342573822165,"sku":"P2B725-11\/8","price":156.2,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/MOTOR-PULLEYS-300x248_9f3aebed-5f10-42e2-944f-da7a3fa15d70.jpg?v=1772652775","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-replacement-motor-pulley-1-3-8-fixed-bore-shaft-7-5-od-2b-grooves","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}