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Repair Guide for String Trimmers

Apr 28, 2025

String Trimmer Repair Notes

Introduction

  • Focus: Repairing a steel string trimmer that won't start.
  • Background: Trimmer belongs to a co-worker at a large facility.
  • Objective: Diagnose and repair the trimmer, acknowledging that solutions may vary between models.

Initial Diagnosis

  • Observation: Trimmer doesn’t start; previous extensive cleaning allowed a temporary start.
  • Assumption: The engine and ignition system are fine; issues likely with the carburetor or fuel.

Fuel Inspection

  • Step: Pour out current fuel to check for staleness or water.
  • Findings: Fuel not stale, no water detected.
  • Conclusion: Fuel quality not the issue, focus shifts to other components.

Component Inspection

  • Fuel Filter: Steel-branded filter present, avoids aftermarket fitting issues.
  • Spark Arrester Screen: Inspected for clogging; enough carbon to warrant cleaning.
    • Cleaning Method: Torch used to burn off carbon.
  • Valve Clearance: Checking clearance as it affects starting.
    • Procedure: Use a shim to measure clearance; maintain precise alignment.

Spark Plug

  • Condition: Appears oily.
  • Cleaning Method: Burn off oil with fire, check gap (target 20 thousandths); action taken if needed.

Carburetor Inspection

  • Carburetor Type: Not advanced but serviceable.
  • Fuel Adjustment Screws: Still present, unlike newer models.
  • Impulse Line: Works the pump; crucial for operation.

Carburetor Components

  • Inlet Screen: Checked for debris; found clear.
  • Diaphragm: Inspected for functionality.
    • Issue: Diaphragm too stiff, impairs operation.
    • Solution: Considered aftermarket carburetor due to high OEM costs.

Decision-Making

  • Aftermarket Carb Choice: Based on cost-effectiveness despite perceived quality issues.
    • Price Comparison: Aftermarket ($20) vs. OEM (3x cost).
    • Risk: Low success rate with old carb; opted for new carb.

Installation & Testing

  • New Carb Installation: Replace gasket, install carb, ensure clearance with fuel tank.
  • Air Filter: Install new filter and cover.
  • Fuel System Test: Verify purge bulb operation.

Final Test

  • Outcome: Trimmer started and ran; minor idle adjustment needed.
  • Verification: Conduct cool-down and re-start test for reliability.

Closing Thoughts

  • Budget Constraints: Emphasis on practicality over perfection.
  • Alternative Actions: Discuss options with owner, respect financial limits.
  • Personal Preference: Would choose aftermarket even for personal trimmer.

Conclusion

  • Reflection: Decisions made with financial sensibility.
  • Open Invitation: Encourage questions and further discussion on similar repair projects.

Thank you for watching and engaging with this repair process.

Full transcript