{"product_id":"castair-repacement-motor-pulley-1-3-8-fixed-bore-shaft-6-25-od-2b-grooves-p2b625-13-8","title":"Castair, Repacement Motor Pulley 1 3\/8\" Fixed Bore Shaft 6.25\" OD. 2B Grooves P2B625-13\/8","description":"\u003cp\u003eThe Castair P2B625-13\/8 is a 2-groove (2B) replacement motor pulley with a fixed 1-3\/8\" bore shaft and 6.25\" outer diameter, built for Cast Air belt-drive air compressor systems. If your existing motor pulley is worn, cracked, or out of spec, this is the direct replacement — same groove profile, same bore, same OD — so you can get your compressor back in service without fabricating or modifying anything.\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 below are drawn from the product listing and standard 2B-groove pulley engineering conventions. Contact us if you need confirmation for a specific compressor application.\u003c\/p\u003e\n\n\u003ch2\u003eWhat Is a 2B Motor Pulley?\u003c\/h2\u003e\n\u003cp\u003eThe 2B designation tells you this pulley has two B-section V-belt grooves. B-section belts are the standard for single-phase and three-phase compressor motors in the 1-5 HP range. Two grooves let you run a matched belt pair, which doubles the power transmission capacity versus a single-groove setup and reduces belt slip under load — important for compressors that cycle frequently in a busy shop.\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 6.25\"\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 Castair belt-drive compressor systems using 1-3\/8\" motor shafts and B-section belts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P2B625-13\/8\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Motor Pulley OD Matters for Compressor Performance\u003c\/h2\u003e\n\u003cp\u003eThe motor pulley OD and the pump flywheel OD together define the belt drive ratio — and that ratio determines how fast the compressor pump turns. A 6.25\" motor pulley paired with a larger flywheel on the pump creates the speed reduction needed to run most single-stage Cast Air pumps at their correct RPM (typically 900-1,100 RPM on the pump side). Using the wrong pulley OD shifts this ratio, which can over-speed the pump and shorten its life, or under-speed it and cost you CFM. Always verify the OD matches the original before ordering.\u003c\/p\u003e\n\n\u003ch3\u003eFixed Bore vs. Taper-Lock (SK\/SD) Pulleys\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eFixed bore pulleys\u003c\/strong\u003e like the P2B625-13\/8 are machined to a specific shaft diameter — in this case 1-3\/8\". They mount directly to the motor shaft with a keyway and set screw. The correct choice for a direct replacement on an existing motor with the same shaft diameter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTaper-lock (SK\/SD) pulleys\u003c\/strong\u003e use a separate bushing that allows one pulley to fit multiple shaft diameters. Preferred when future motor swaps are anticipated or shaft diameter may vary.\u003c\/li\u003e\n\u003cli\u003eIf your original pulley was a fixed bore 1-3\/8\", the P2B625-13\/8 is the drop-in replacement. Do not substitute a taper-lock pulley — they require matching bushings and the hub geometry differs.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen Does a Shop Need This Pulley?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eMotor pulley cracked, damaged, or showing V-belt groove wear causing belt slippage or squealing\u003c\/li\u003e\n\u003cli\u003eReplacing a motor where the new motor has a 1-3\/8\" shaft — this pulley restores the original drive ratio\u003c\/li\u003e\n\u003cli\u003eRebuilding a Cast Air belt-drive compressor and sourcing OEM-spec replacement parts\u003c\/li\u003e\n\u003cli\u003eCompressor pump RPM is off (verified with a tachometer) and pulley OD needs correction\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003e2B Fixed-Bore 1-3\/8\" Motor Pulley Size Comparison\u003c\/h3\u003e\n\u003cp\u003eCast Air offers this pulley in multiple OD sizes. Here is how the 2B fixed-bore 1-3\/8\" bore lineup compares:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B625-13\/8 — 6.25\" OD — $68.34\u003c\/strong\u003e (this unit) — smallest in the series; lowest pump RPM for a given motor speed\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B675-13\/8 — 6.75\" OD — $71.23\u003c\/strong\u003e — slightly larger diameter, increases pump speed for the same motor RPM\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B80-13\/8 — 8.0\" OD — $88.55\u003c\/strong\u003e — larger pulley, higher pump RPM, used on higher-CFM applications\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP2B875-13\/8 — 8.75\" OD — $103.95\u003c\/strong\u003e — largest in the fixed-bore 1-3\/8\" lineup\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eMeasure the original pulley OD before ordering. If you are not sure, call us — we can help verify the correct replacement for your Cast Air compressor model.\u003c\/p\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P2B625-13\/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 6.25\"\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 Compatibility:\u003c\/strong\u003e B-section V-belts (two grooves, matched pair)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $68.34\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 P2B625-13\/8 motor pulley\u003c\/li\u003e\n\u003cli\u003eSet screw(s) for shaft retention\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eBelts are not included. Order the appropriate B-section matched belt pair separately for your drive length.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h2\u003e\n\u003cp\u003eWe have specialized in Cast Air compressor parts and accessories since 2016. When you order from us, you get the correct part — not a generic substitute that may not match your groove profile or bore diameter. Our team knows the Cast Air lineup and can confirm fitment before you order. Every order ships free, and our tech support line is staffed by people who know compressor drive systems.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCast Air specialist\u003c\/strong\u003e since 2016 — not a general parts warehouse\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 — call before you order if you are not sure about fitment\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e on all Cast Air parts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHonest guidance\u003c\/strong\u003e — we will tell you if a different size is the right call 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":53342573428949,"sku":"P2B625-13\/8","price":126.38,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/MOTOR-PULLEYS-300x248_322f19ea-1fc4-4a5f-9ac2-3902bff118d6.jpg?v=1772652771","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-repacement-motor-pulley-1-3-8-fixed-bore-shaft-6-25-od-2b-grooves-p2b625-13-8","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}