Why Some Brand‑New Kubota Excavators Feel Slow

[MikePhua]

Reported Symptoms from Owners

• A user who purchased a brand-new Kubota U55 and a U27 reported very sluggish performance, especially in boom lift and slew speed, compared to other brands they’ve used.
  
• Even in “Normal” mode, the U55 felt about as slow as a competitor’s ECO mode — and the Kubota’s ECO mode seemed nearly unusable for productive work.
  
• The same person noted very limited foot space and an uncomfortable seat height, which made operation less enjoyable.
  

Possible Causes

1. Hydraulic Flow Restriction or “Limiting Valve”
   • One commenter suggested the machine might have a high-pressure (HP) limiting valve that’s set overly conservatively, which could reduce available hydraulic flow to the boom or swing.
     
   • The dealer reportedly said there are built-in restrictions on the pilot (joystick) controls to “allow the machine to operate smoother” — but that comes at the cost of speed.
     
2. Computer-Controlled ECO Mode
   • Rather than lowering engine RPM in ECO mode, Kubota seems to rely on its hydraulic system to enforce speed limits, slowing down movements without reducing engine speed.
     
   • This suggests a software‑limited hydraulic profile rather than a purely mechanical constraint.
     
3. User Perception vs. Spec
   • Another experienced operator noted that newer Kubota machines are very quiet, so “slow” may be relative — the machine could be working correctly, but feels slower because it’s not noisy or aggressive.
     
   • He also recommended checking published hydraulic specs (flow rates, slew/boom speed) and confirming that the engine is indeed reaching rated RPM under load.
     

Similar Reports on Other Kubota Models

• On a Kubota KX018‑4, an owner described slow boom, bucket, and travel movements; they also observed cavitation noise in a pump line and air bubbles in the hydraulic tank, indicating potential air ingress or internal leakage.
  
• Another user on a different platform noted that when a Kubota KX33 got hot, the boom’s speed dropped — likely due to hydraulic fluid thinning or a control valve not maintaining pressure.
  

Technical Explanation

• Pilot-Control Hydraulics: Many modern Kubota excavators use pilot-operated hydraulic control. This means the joysticks don’t directly move the valves — instead, they send electrical or hydraulic signals to a control valve block, which then meters flow. If that system is tuned for “smoothness,” there can be less instantaneous responsiveness.
  
• Pressure Limiter or Flow Regulator: It’s possible a limiter (either factory-set or adjustable) is reducing maximum hydraulic flow to ensure longevity or fuel efficiency.
  
• Hydraulic Fluid Temperature Effect: As hydraulic fluid heats, its viscosity drops. If the system isn’t designed to compensate aggressively, you’ll feel slower action when the machine is hot.
  
• Air in Hydraulic System: Entrained air can compress, causing delayed or weak hydraulic response until the system bleeds itself.
  

What to Do About It

• Ask your dealer if a service tool or handheld programmer can adjust hydraulic parameters. Some brands allow flow/response tuning.
  
• Request your dealer check system pressure (hydraulic test) under load to see whether the limits are mechanical or software-based.
  
• Use a scan tool or monitor to verify engine RPM during operations — maybe the engine isn’t reaching full speed under load.
  
• Talk to other owners or forums (for example on OrangeTractorTalks) to see whether others have similar machines and how they resolved “feel slow” complaints.
  
• If you suspect air, inspect for loose fittings or low hydraulic fluid, and bleed the system completely.
  

Practical Example (Real-World Use)
One contractor reported that after 185 hours, his U55 felt painfully slow, especially compared to machines he rented. He considered programming adjustments but the dealer said nothing could be changed in the main functions — likely meaning the machine had software or internal valve limits.
Machine to Reference
An example of a comparable machine is the Kubota CFG‑40UF Mini Excavator, which illustrates the type of compact hydraulically controlled Kubota excavator where similar flow or control issues might be noticed by operators.
Conclusion
Sluggish performance on brand-new Kubota excavators often comes down to how the hydraulic system is tuned — especially in ECO mode — as well as possible flow-limiting valves or software restrictions. While this may impact operational speed, it could also reflect a design choice for smoother control and increased longevity. If you experience it, work with your dealer to test and possibly adjust those hydraulic parameters, and make sure the machine is operating within its intended spec rather than assuming it's faulty.