RKA4G35NL-CR | Gearbox Pump, 4 GPM 3500 PSI, Fits 1697 Gas Engine

RKA4G35NL-CR | Gearbox Drive Pump System — 4 GPM @ 3500 PSI

The RKA4G35NL-CR gearbox-drive pump system is a professional-grade triplex plunger pump engineered
specifically for small OEM builders, equipment fabricators, and DIY contractors who want to build
their own high-performance pressure washer or sewer jetter while saving hundreds of dollars compared
to preassembled equipment packages.

This is NOT a left-hand or reverse-drive pump. The RKA4G35NL-CR is a standard rotation pump
equipped with a factory-installed gearbox drive (CR) that directly attaches to gasoline or diesel
engines with a 1-inch solid crankshaft. The gearbox provides proper speed reduction and alignment,
delivering professional reliability and long service life right out of the box. The factory-installed
gearbox represents an added value of approximately $90 and eliminates the need for complicated
drive calculations, coupler selection, or alignment procedures.

This RKA4G35NL-CR pump system is a favorite among small equipment manufacturers, pressure washing contractors, and
mobile service professionals because it offers a simple and affordable path to building powerful,
engine-driven cleaning equipment.

Engine Compatibility

The RKA4G35NL-CR gearbox drive is designed to bolt directly to common horizontal-shaft engines with a
1-inch crankshaft. Recommended engines include:

• Honda GX390 389cc OHV engine
• Predator 420cc OHV engine
• Predator 459cc OHV engine
• Other compatible gasoline or diesel engines with a 1-inch horizontal shaft

This compatibility allows builders to source engines locally and create custom cleaning systems
tailored to their specific needs and budgets.

Key Specifications

• Flow Rate: 4.0 GPM
• Pressure Rating: 3,500 PSI
• Pump Speed: 1,750 RPM (gearbox reduced)
• Drive Type: Factory-installed gearbox (CR)
• Engine Connection: 1-inch solid crankshaft
• Pump Head: Nickel-plated forged brass
• Plungers: Solid ceramic
• Bearings: Oversized ball bearings
• Valves: Stainless steel
• Warranty: 5-year commercial warranty

Why the Factory Gearbox Matters

The integrated CR gearbox is one of the most important advantages of this pump system. Direct-drive
pumps often run at engine speed, which can increase wear and reduce service life. Belt-drive systems
require alignment, tensioning, and additional hardware. The RKA4G35NL-CR gearbox provides the ideal
middle ground by reducing engine RPM to the pump’s optimal 1,750 RPM operating speed.

• Extends pump life by reducing heat and friction
• Reduces vibration compared to direct-drive systems
• Eliminates the need for belts and pulleys
• Simplifies installation for DIY builders
• Ensures proper alignment between engine and pump

This design makes professional-grade performance accessible to contractors building their own
equipment for the first time.

What’s Included

• RKA triplex plunger pump
• Factory-installed gearbox drive
• Pre-installed break-in oil
• Vented dipstick
• Oil sight glass
• Owner’s manual and schematic
• Factory performance test sheet
• 5-year commercial warranty

How the Pump Works

The RKA series triplex pump uses three ceramic plungers driven by a precision crankshaft and
connecting rod system. As the plungers reciprocate, water is drawn into the pump through stainless
steel inlet valves and discharged at high pressure through the outlet valves. This triplex design
provides smoother flow, reduced pulsation, and improved durability compared to axial or wobble
plate pumps.

The gearbox reduces engine speed to the pump’s optimal operating range, allowing the pump to run
cooler and last significantly longer while maintaining full cleaning power.

Built for DIY Contractors & Small OEM Builders

The RKA4G35NL-CR is especially popular among builders who want to create their own pressure washer
or sewer jetter systems. By combining this pump with a compatible engine, hose reel, frame, and
accessories, contractors can assemble professional-grade equipment at a fraction of the cost of
factory-built machines.

This approach gives builders complete control over system layout, accessories, and final cost while
still using commercial-grade components.

Expanded Application Ideas

DIY Pressure Washer Builds

• Skid-mounted pressure washer systems
• Truck-bed cleaning rigs
• Trailer-mounted wash systems
• Portable contractor cleaning units
• Fleet washing setups

DIY Sewer Jetter Systems

• Drain cleaning machines
• Pipe jetting equipment
• Septic service rigs
• Grease trap cleaning systems
• Municipal jetter builds

Contractor Cleaning Equipment

• Concrete cleaning and surface prep
• Deck and fence restoration
• Roof cleaning systems
• Graffiti removal rigs
• Heavy equipment washing

Fleet & Equipment Maintenance

• Truck and trailer wash systems
• Rental equipment cleaning
• Construction equipment washdown
• Farm and agricultural machinery cleaning

Agricultural Applications

• Barn and livestock facility cleaning
• Farm equipment sanitation
• Irrigation maintenance
• Sprayer washout systems

Industrial & Commercial Uses

• Property maintenance cleaning
• Parking garage washing
• Warehouse sanitation
• Manufacturing facility cleaning

Advantages Over Buying a Complete Machine

• Save hundreds of dollars compared to prebuilt units
• Choose your preferred engine brand and accessories
• Customize layout and frame design
• Upgrade components as your business grows
• Learn and control your equipment inside and out

Summary

The RKA4G35NL-CR gearbox-drive pump system offers the perfect foundation for building professional
cleaning equipment. With its factory-installed gearbox, direct engine compatibility, and commercial
triplex pump design, it delivers the performance and durability contractors demand without the cost
of prebuilt machines. Whether building a pressure washer, sewer jetter, or custom cleaning system,
this pump provides the reliability, flexibility, and value that make DIY equipment building both
practical and profitable.