The Castair PK50 is a 2 HP single-stage V-twin (V-2) cylinder bare pump with a 10" (1A-series) flywheel and 16 oz. oil capacity. This is the step up from the single-cylinder PK20/PK30 pumps — two cylinders in a V-configuration deliver more CFM per revolution and smoother compression than a single-cylinder design. The PK50 is the correct replacement pump when your existing Cast Air two-cylinder compressor pump has failed and the motor and tank are still serviceable.
Note: Cast Air did not provide a dedicated manufacturer product page for this pump. Specifications are drawn from the product listing. Call us to confirm CFM output, max PSI rating, and motor/pulley compatibility for your application before ordering.
V-2 Cylinder Configuration — What It Adds Over Single-Cylinder
A V-2 (V-twin) pump has two cylinders arranged in a V formation sharing a common crankshaft. Each cylinder fires on alternate half-strokes of the crankshaft, which means the pump compresses air more continuously than a single-cylinder design — the compression strokes are more evenly distributed over each crankshaft revolution. The practical result is:
- Higher CFM output for the same motor RPM compared to a single-cylinder pump of equivalent bore
- Smoother operation with less vibration (more balanced compression load)
- Lower peak torque demand per stroke on the motor and belt drive
- More consistent tank pressure recovery under load
For a shop running air tools intermittently — impacts, ratchets, die grinders — the V-2 design keeps up better with cycling demand than a single-cylinder at the same HP rating.
Pump Specification Details
- Part Number: PK50
- HP Rating: 2 HP
- Stage: Single stage
- Cylinders: 2 (V-2 configuration)
- Flywheel OD: 10" (1A-series flywheel)
- Oil Capacity: 16 oz.
- Drive: Belt drive
- Price: $371.91
Oil Capacity and Maintenance
The PK50 uses 16 oz. of compressor oil — double the PK20/PK30 capacity, reflecting the larger crankcase required for the V-2 configuration. Oil maintenance is critical:
- Check oil level before each startup — a V-2 pump with low oil will seize the crankshaft bearings quickly under load
- Change oil at Cast Air's specified interval (confirm with documentation or call us)
- Use compressor pump oil specific to Cast Air or compatible oil-lubricated pump service
- Overfilling causes oil carry-over into the air stream — stay within the specified fill range
When Does a Shop Need the PK50 vs. PK30?
The PK30 is 1.5 HP, single-cylinder. The PK50 is 2 HP, V-2 cylinder. Choose the PK50 when:
- Your existing compressor is V-2 configuration and the pump has failed — the PK50 is the replacement
- You are building a new belt-drive compressor and need more CFM than a single-cylinder 1.5 HP pump provides
- Air tool demand in the shop has grown and the single-cylinder pump cannot keep up with duty cycles
- The motor is rated at 2 HP or higher and the single-cylinder pump is the bottleneck
If your existing compressor is single-cylinder and you are considering upgrading to PK50, confirm that the motor is rated for 2 HP — underpowering a V-2 pump will overload the motor on startup. The motor and pump HP ratings must match.
Cast Air Bare Pump Comparison
- PK20 — 1.5 HP, 1-cylinder, 7.5" flywheel, 8 oz. — $194.81
- PK30 — 1.5 HP, 1-cylinder, 10" flywheel, 8 oz. — $241.01
- PK50 — 2 HP, V-2 cylinder, 10" flywheel, 16 oz. — $371.91 (this unit) — higher CFM, V-2 smoothness
- PK60 — 3.5 HP, V-2 cylinder, 10" flywheel, 32 oz. — $432.74 — heavy shop production use
Technical Specifications
- Part Number: PK50
- Manufacturer: Cast Air (Castair)
- HP: 2
- Stage: Single stage
- Cylinders: 2 (V configuration)
- Flywheel OD: 10" (1A-series)
- Oil Capacity: 16 oz.
- Drive Type: Belt drive (flywheel included, belt not included)
- Price: $371.91
- CFM/PSI Rating: Not confirmed in listing — call for current performance data
- Manufacturer Data: Product page not available — specifications from product listing data
What Is Included
- 1x Castair PK50 V-2 bare pump with 10" flywheel
Motor, motor pulley, belt, tank, pressure switch, safety valve, and connecting hardware are not included. This is the pump assembly only. Confirm motor compatibility (2 HP minimum, correct RPM and shaft size) before purchasing.
Why Buy From Air Compressor Factory Direct?
A V-2 pump replacement involves more compatibility checks than swapping a simple single-cylinder unit — motor HP, shaft size, motor pulley, belt length, and tank capacity all need to match or be adjusted. We have been working with Cast Air pump assemblies since 2016 and can help you confirm the complete component list before you order. Free shipping, free tech support, full manufacturer warranty on all Cast Air parts.
- Cast Air specialist since 2016
- Free shipping on all orders
- Free tech support — we help you build the correct component list
- Full manufacturer warranty
- Application guidance — we confirm motor compatibility before you commit
Call 866-217-0063 for quick answers and help!
