{"product_id":"castair-4-5-hp-single-stage-w3-cylinder-air-compressor-bare-pump-with-10-1a-flywheel-od-28-oz-oil-capacity","title":"Castair 4-5 HP Single Stage W3 Cylinder Air Compressor Bare Pump with 10 - 1A Flywheel OD, 28 oz. Oil Capacity","description":"\u003cp\u003eThe Castair PUK65 is a 4 to 5 HP single-stage cast-iron bare pump with a W3 (three-cylinder) configuration, 10-inch 1A flywheel, and 28-ounce oil capacity. It weighs 70 pounds. This is the pump for building a custom compressor unit from major components, replacing a failed pump in an existing tank-and-motor setup, or upgrading from an underpowered pump to a larger cylinder configuration. At $605.99, the PUK65 is the starting point for a serious piston compressor build in the 4-5 HP range.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Cast Iron vs. Aluminum\u003c\/h2\u003e\n\u003cp\u003eCast-iron cylinders dissipate heat better than aluminum, resist bore wear longer, and hold machined tolerances through thousands of thermal cycles. An aluminum pump on a busy shop compressor runs hotter, wears the bore faster, and loses compression ring seal earlier. Oil-less pumps avoid lubrication maintenance entirely but sacrifice longevity significantly — Castair specifies that their cast-iron oil-lubricated pumps offer up to 10 times the service life of oil-less designs. For a production shop or contractor running this pump daily, the cast-iron construction pays for the price difference within the first couple of years of service through reduced downtime and parts replacement.\u003c\/p\u003e\n\n\u003ch3\u003eKey Specifications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHP rating:\u003c\/strong\u003e 4 to 5 HP (motor supplied separately)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStage:\u003c\/strong\u003e Single stage\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCylinder configuration:\u003c\/strong\u003e W3 (three cylinder)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlywheel:\u003c\/strong\u003e 10-inch diameter, 1A\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOil capacity:\u003c\/strong\u003e 28 oz\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 70 lbs\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWarranty:\u003c\/strong\u003e 1 year parts when properly installed and maintained\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $605.99\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eConstruction Features\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCast-iron cylinder construction:\u003c\/strong\u003e Superior heat dissipation and wear resistance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eW3 cylinder design:\u003c\/strong\u003e Three-cylinder configuration for smooth airflow and compact dimensions relative to output\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTwo-piece connecting rod:\u003c\/strong\u003e Independent wrist pin for proper oil distribution and reduced piston side loading\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eThree-ring piston:\u003c\/strong\u003e Oil control, compression, and wiper rings for clean, efficient compression\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBall bearings at crankshaft ends:\u003c\/strong\u003e Reduced friction and longer bearing service life\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e10-inch flywheel:\u003c\/strong\u003e Proper belt drive sizing for 4-5 HP motor range and standard single-groove belt\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e28-oz oil capacity:\u003c\/strong\u003e Adequate for extended run cycles without overheating the crankcase oil\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCastair Bare Pump Lineup — Where the PUK65 Fits\u003c\/h2\u003e\n\u003cp\u003eCastair publishes the following bare pump options. The PUK65 sits in the middle of the single-stage range:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePK20\u003c\/strong\u003e — 1.5 HP, 20 lbs, single, 1 cyl, 7.5\" flywheel, 8 oz oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePK30\u003c\/strong\u003e — 1.5 HP, 45 lbs, single, 1 cyl, 10\" flywheel, 8 oz oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePK50\u003c\/strong\u003e — 2 HP, 50 lbs, single, V2 cyl, 10\" flywheel, 16 oz oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePK60\u003c\/strong\u003e — 3.5 HP, 55 lbs, single, V2 cyl, 10\" flywheel, 24 oz oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePUK65\u003c\/strong\u003e — 4-5 HP, 70 lbs, single, W3 cyl, 10-1A flywheel, 28 oz oil ($605.99) — this unit\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVA80\u003c\/strong\u003e — 3.5-5 HP, 110 lbs, single, V2 cyl, 12.5-2A flywheel, 1 qt oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eC1\u003c\/strong\u003e — 4-7.5 HP, 225 lbs, two-stage, inline 2 cyl, 16.875\" flywheel, 2 qt oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eC2\u003c\/strong\u003e — 7.5-10 HP, 320 lbs, two-stage, V4 cyl, 19.0\" flywheel, 2 qt oil\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen Do You Need the PUK65 vs. Adjacent Pumps?\u003c\/h2\u003e\n\u003cp\u003eThe PUK65 is correct when you have a 4 or 5 HP motor and need a matched single-stage pump. The W3 cylinder design makes it more compact than the VA80, which uses a larger V2 configuration at similar HP ratings — useful when fitting into an existing belt-guard configuration where space is constrained. If your motor is 3.5 HP, the PK60 is a better match. If you need two-stage compression — for working pressures above 125 PSI or better efficiency at high continuous output — step to the C1.\u003c\/p\u003e\n\u003cp\u003eFor a replacement application, match the flywheel diameter to your existing belt guard and sheave setup. The PUK65 uses a 10-inch 1A flywheel, which fits the standard belt arrangements on Castair units in the 4-5 HP range. Confirm your pulley groove count before ordering.\u003c\/p\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e PUK65\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Castair (Cast Air)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHP range:\u003c\/strong\u003e 4-5 HP\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStages:\u003c\/strong\u003e Single\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCylinders:\u003c\/strong\u003e W3 (three-cylinder)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFlywheel OD:\u003c\/strong\u003e 10\" — 1A\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOil capacity:\u003c\/strong\u003e 28 oz\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 70 lbs\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWarranty:\u003c\/strong\u003e 1 year parts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $605.99\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1x Castair PUK65 cast-iron bare pump with 10-inch flywheel installed\u003c\/li\u003e\n\u003cli\u003eNote: Motor, tank, pressure switch, belts, and motor pulley are sold separately\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cp\u003eWe carry Castair bare pumps for build and replacement work. If you are building a compressor from components or replacing a failed pump, call us before ordering — we can confirm the PUK65 is the right pump for your motor HP and RPM rating, and check whether you need matching belts and pulleys for your specific setup. Free shipping on qualifying orders. Full Castair warranty applies.\u003c\/p\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":53342575493333,"sku":"PUK65","price":1117.54,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/CastAirTwoStageAirCompressorPump_959610fd-1129-44df-ba49-6443f947673c.png?v=1772652809","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-4-5-hp-single-stage-w3-cylinder-air-compressor-bare-pump-with-10-1a-flywheel-od-28-oz-oil-capacity","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}