Adjusting Hydraulic Pump Pressure on the Kobelco SK200 Excavator

[MikePhua]

The Kobelco SK200 and Its Hydraulic Architecture
The Kobelco SK200 is one of the most widely deployed mid-size hydraulic excavators in Asia and the Middle East, known for its balance of power, fuel efficiency, and responsive hydraulics. Manufactured by Kobelco Construction Machinery, a division of Kobe Steel founded in 1930, the SK200 series has evolved through multiple generations, with the -1 and -2 variants being particularly common in legacy fleets.
The SK200 uses a variable displacement axial piston pump to supply hydraulic flow to its boom, arm, bucket, swing, and travel circuits. These pumps are pressure-compensated and load-sensing, meaning they adjust output based on demand. The system includes a main relief valve, pilot control circuits, and electronic feedback from sensors and solenoids. Adjusting pump pressure is a delicate operation that requires understanding both mechanical and hydraulic principles.
Why Adjust Hydraulic Pressure
Operators may seek to adjust hydraulic pressure for several reasons:

• Reduced digging force or sluggish boom response
  
• Inconsistent travel speed or swing torque
  
• Aftermarket attachment requiring higher flow or pressure
  
• Compensation for internal leakage or aging components
  

However, increasing pressure beyond factory specifications can damage seals, hoses, and valve blocks. It may also void warranties or trigger fault codes in newer machines with electronic control modules.
Preliminary Checks Before Adjustment
Before attempting any pressure adjustment, technicians should perform a full diagnostic:

• Measure current system pressure using a calibrated gauge at the test port
  
• Compare readings against factory specs (typically 320–350 bar for main pump)
  
• Inspect pilot pressure (usually 40–50 bar) and control signal voltage
  
• Check for clogged filters, worn pump components, or leaking cylinders
  
• Confirm that the relief valve is functioning and not stuck open
  

One field mechanic in Western Australia emphasized that adjusting pressure without diagnosing the root cause is “like seeking something in the dark.” A sluggish boom may be due to a leaking cylinder or blocked return line—not low pump pressure.
Locating the Adjustment Point
On the SK200, the main pump pressure is typically adjusted via a hex-head screw or bolt located on the pump body near the regulator valve. This screw interfaces with a spring-loaded spool that sets the maximum displacement pressure.
Adjustment steps:

• Shut down the machine and relieve hydraulic pressure
  
• Locate the adjustment screw on the pump (often marked or color-coded)
  
• Turn clockwise to increase pressure, counterclockwise to decrease
  
• Make small adjustments (¼ turn at a time) and recheck pressure
  
• Monitor system behavior under load and verify with pressure gauge
  

Some models may require removing a lock nut before adjustment. Always refer to service documentation or consult a technician familiar with Kobelco systems.
Relief Valve Settings and Safety Considerations
The main relief valve protects the system from overpressure. It is usually mounted on the valve block or integrated into the pump housing. Adjusting this valve changes the maximum allowable pressure before bypass occurs.
To adjust:

• Identify the relief valve (often a large hex plug with internal spring)
  
• Use a torque wrench to avoid over-tightening
  
• Monitor pressure rise during operation and ensure it stays within safe limits
  
• Never exceed manufacturer-recommended settings (typically 350 bar)
  

Exceeding relief pressure can cause catastrophic failure. One operator reported cracking a valve block after increasing pressure without adjusting the relief valve, resulting in a costly rebuild.
Electronic Controls and Feedback Loops
Later SK200 models include electronic pressure regulators and solenoids that modulate pump output based on joystick input and load sensing. These systems use feedback from pressure sensors and may override manual adjustments.
If the machine includes electronic control:

• Check solenoid voltage and signal continuity
  
• Inspect sensor wiring and connector pins for corrosion
  
• Use diagnostic software to view pressure setpoints and error codes
  
• Avoid manual adjustment unless electronic override is disabled
  

In some cases, a faulty sensor may cause the pump to derate, mimicking low pressure. Replacing the sensor restores normal function without touching the pump.
Recommendations for Field Technicians
To safely adjust hydraulic pressure on the SK200:

• Use certified gauges and tools
  
• Document all changes and return to baseline if performance worsens
  
• Replace seals and hoses rated below new pressure settings
  
• Train operators to recognize signs of overpressure (e.g., jerky motion, hose bulge)
  
• Consult factory service manuals or experienced mechanics before proceeding
  

Technicians should also consider environmental factors. High ambient temperatures can thin hydraulic oil, reducing effective pressure. Using the correct viscosity and maintaining clean filters improves system stability.
Conclusion
Adjusting hydraulic pump pressure on the Kobelco SK200 is a precision task that requires mechanical insight, diagnostic discipline, and respect for system limits. While performance gains are possible, they must be balanced against safety and longevity. With proper tools and informed technique, operators can restore responsiveness and adapt the machine to evolving jobsite demands. In hydraulic systems, pressure is power—but only when applied wisely.