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Diagnosing Weak Saw Head on Hydro-Ax 611E Feller Buncher
#1
Introduction
For operators of the Hydro-Ax 611E feller buncher, a sluggish or underperforming saw head can be a real headache. When the 22-inch saw only manages to cut through small-diameter trees and takes long to spin back up—despite throttle fully engaged—it’s time to dig into diagnostics. Understanding whether the culprit is the hydraulic pump or the motor is crucial for restoring proper cutting performance.
Machine Background and Specs
The Hydro-Ax 611E is a wheel feller buncher from the Hydro-Ax lineup, widely recognized for combining robust power with forestry-specific functionality.
Typical machine specs include:
  • Operating length: 26 ft 7 in
  • Width: 9 ft 3 in
  • Height: 10 ft 4 in
  • Weight: 25,800 lb
Many units were outfitted with Cummins 6BT engines and saw heads like the Risley 21-inch, although setups could vary .
Possible Causes of Weak Saw Performance
Diagnosing slow saw spin and cutting failure typically directs attention to either hydraulic flow/pressure limitations or wear inside the saw’s hydraulic motor.
The usual suspects include:
  • Hydraulic pump delivering insufficient flow or pressure
  • Valve block or control valve partially blocked or leaking
  • Damaged hoses, fittings, or internal leakage
  • Worn or internally compromised saw head motor
Diagnostics—What You Can Check Yourself
To avoid costly diagnostics fees, here’s how you can test the system at home:
  • Use pressure gauges on the saw circuit to compare against manufacturer specs (often found in service manuals).
  • Measure hydraulic flow during saw engagement using a flow meter—confirm it meets spec.
  • Inspect hoses and fittings for leaks or restrictions. Low flow could be due to collapsed lines or partially blocked filters.
  • Observe motor behavior: if the pump delivers adequate pressure but the saw still spins slowly, the hydraulic motor may be failing internally.
Terms to Know
  • Hydraulic pump: Converts engine power into hydraulic pressure; if flow drops, performance suffers.
  • Hydraulic motor: Converts pressurized fluid into mechanical rotation for the saw blade. Internal wear lowers output.
  • Flow/Pressure gauge: Tool for measuring system’s hydraulic values.
  • Internal leakage: When hydraulic fluid bypasses internal seals, reducing torque and speed.
Advice from Experts and Owners
While direct quotes from the original discussion are unavailable, diagnostics advice from similar cases emphasizes measuring pump output and inspecting control valves. This aligns with professional guidance to check both flow and internal integrity before replacing components .
Illustrative Anecdote
A regional logger once shared that he assumed his saw motor was failing. He installed gauges, only to find that pressure was sagging under load—an underperforming pump was the real issue. After replacing the worn pump, the saw immediately regained speed and power, capable now of cutting 18- to 20-inch trees consistently where before it stalled at 8 or 10 inches.
Recommendations & Prevention
  • Start simple: Gauge the saw circuit pressure and flow first—this often reveals whether the pump is underperforming.
  • Compare to specs: Use the service manual or trusted references for expected readings.
  • Check hoses and valves: Clean or replace clogged filters, repair leaks, and ensure control valves shift fully.
  • Evaluate motor condition: If hydraulic input is normal but saw is sluggish, consider motor wear or internal contamination.
  • Regular maintenance: Keep hydraulic fluid clean, filters changed, and hoses inspect­ed to extend component life.
Conclusion
A weak Hydro-Ax 611E saw head that struggles to start or cut properly may result from a failing pump, restricted flow, or worn saw motor. With methodical testing—gauging flow and pressure, inspecting components, and comparing to specs—you can pinpoint the problem without expensive service calls. A well-informed and hands-on approach restores performance and keeps your machine operating effectively.
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