The Pro 50-4S: 4-Stroke Power. Zero Mix.
Powered by Honda. Built by NorthRock.
- Honda GXH50 Engine: A commercial-grade 4-stroke engine means quieter operation, better fuel efficiency, and no fuel mixing.
- Quick Disconnect System: Every unit comes standard with a quick disconnect adapter. Switch shafts in seconds without tools—just lift the spring pin and twist.
- Operator Comfort: The custom 440AV1 Frame Assembly features ergonomic padding and a 4-point engine mount system to isolate vibration from the operator's back.
- Universal Fit: The transmission box (Part 635A1) is designed to drive standard flexible shafts, allowing you to use your existing inventory of heads and shafts
- Reliable starts and consistent 10,000 VPM consolidation power. Designed with a heavy-duty steel frame and breathable padding, it’s built for all-day pours.
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Unit Specifications
| Model | Pro 50-4S |
| Engine | Honda GXH50 (4-Stroke) |
| Horsepower | 2.5 HP (50cc) |
| Vibration Frequency | 10,000 VPM |
| Transmission | High-efficiency synchronous belt drive; Cast aluminum housing |
| Clutch System | Centrifugal clutch with double shielded bearings |
| Flexible Shaft Lengths | 7 ft, 10 ft, 14 ft (Standard) - Up to 21 ft available |
| Compatible Heads | 3/4", 1", 1-1/4", 1-1/2", 1-3/4", 2", 2-1/2" |
Head Performance & Selection Guide
| Head Diameter | Centrifugal Force | Amplitude (Tip) | Radius of Influence | Capacity (y3/hr) |
|---|---|---|---|---|
| 3/4 in (19mm) | 112 lbs | .070 in | 4 in | 4 |
| 1 in (25mm) | 183 lbs | .075 in | 5 in | 6 |
| 1-1/4 in (32mm) | 430 lbs | .080 in | 7 in | 8 |
| 1-1/2 in (38mm) | 760 lbs | .090 in | 14 in | 12 |
| 1-3/4 in (44mm) | 1,100 lbs | .110 in | 18 in | 24 |
| 2 in (51mm) | 1,450 lbs | .130 in | 22 in | 35 |
Configure Your Backpack System
Select your options below to build the perfect kit.
Universal Shaft Adapter Included
Your System Configuration:
*This configuration uses the Universal Adapter to fit all components.
The NorthRock Advantage
Built to outperform the competition with universal compatibility and 4-stroke reliability.
Universal Fit System
Don't let proprietary connections lock you in. Our Universal Counter Shaft accommodates all major brands of vibrators, allowing you to use your existing inventory of heads and shafts with the Pro 50-4S motor.
Honda 4-Stroke Power
Powered by the genuine Honda GXH50. Zero fuel mixing required. Experience quieter operation, easier starts, and significantly reduced emissions compared to standard 2-stroke engines.
True 10,000 VPM
We don't sacrifice power for mobility. Our high-efficiency belt drive transmission maintains a consistent 10,000 VPM, ensuring rapid consolidation even in low-slump concrete mixes.
Operator Comfort
Designed for the long haul. The Pro 50-4S features a custom tubular steel frame with breathable padding and strategic motor mounts that isolate vibration from the operator to reduce fatigue.
Rapid Shipping
No backorders. No waiting on containers. We stock large inventories at our Bohemia, NY facility and ship standard orders typically within 24 hours to keep your job site moving.
Made in USA
Designed, assembled, and supported in the USA. When you call NorthRock for support, you speak to a product expert, not a voicemail box.
Parts & Compatibility Guide
Genuine replacement parts and fitment data for the Pro 50-4S.
System Compatibility
Universal Quick Disconnect
The Pro 50-4S comes standard with a quick disconnect adapter system. This allows the motor to drive NorthRock flexible shafts as well as shafts from other major manufacturers.
- Connection Type: Square drive with spring-pin lock.
- Adapter Included: Yes (Factory Installed).
- Sealant: Requires adhesive sealant on head-end threads for water-tight seal.
Compatible Shaft Lengths
Common Replacement Parts
Refer to the 4-Stroke Backpack Manual for full diagrams.
| Part Name | Part No. |
|---|---|
| Micro V Belt | 390B1 |
| Clutch Spring (Qty 2) | 465D1 |
| Clutch Shoe (Qty 2) | 625A1 |
| Spark Plug (Honda) | CR5HSB |
| Throttle Cable Assembly | 605F1 |
Do I need to mix oil and gas?
No. The Pro 50-4S is powered by a Honda GXH50 4-Stroke engine. You use straight, unleaded gasoline in the fuel tank. This eliminates the need for pre-mixing fuel and reduces smoke and emissions compared to older 2-stroke models.
Can I use shafts from other brands?
Yes. The Pro 50-4S features a Universal Counter Shaft and comes standard with a quick disconnect adapter. This allows you to use Northrock flexible shafts as well as compatible shafts from other major manufacturers. You likely do not need to replace your entire inventory to switch to the Northrock motor.
How do I install or change a shaft?
The unit features a quick disconnect system. To attach a shaft, simply line up the square drive, lift the spring pin on the connector, and insert the adapter. Spin the shaft slightly until the pin clicks into place. No tools are required for daily shaft changes.
What is the maintenance schedule?
Engine: Follow the Honda GXH50 owner’s manual for oil changes and spark plug maintenance
Flexible Shafts: We recommend lubricating the flexible shaft core every 50 hours of operation. Remove the inner core, wipe it clean, and re-coat it with a 1/16" layer of high-quality lithium grease.
Heads: Northrock vibrator heads are factory sealed in an oil bath and require zero maintenance.
What is the maximum shaft length?
The Pro 50-4S is powerful enough to drive flexible shafts up to 21 feet in length. For standard vertical walls and columns, we recommend 10' or 14' shafts.
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