Track Tension Adjustment on Yanmar ViO20 Mini Excavator

[MikePhua]

Proper track tension on the Yanmar ViO20 mini excavator is essential for maintaining undercarriage longevity, preventing derailment, and ensuring efficient travel performance. While the adjustment process is straightforward, overlooking key steps or misjudging sag can lead to premature wear or hydraulic seal failure.
Machine Overview and Undercarriage Design
The Yanmar ViO20 is a zero-tail swing mini excavator designed for tight-access urban and residential excavation. It features a retractable undercarriage, rubber tracks, and a hydraulic track tensioning system. The ViO20’s compact footprint and smooth travel make it popular among landscapers, utility contractors, and rental fleets.
The undercarriage includes:

• Track Frame: Welded steel housing that supports rollers and idlers.
  
• Carrier Rollers: Upper rollers that guide the track over the frame.
  
• Bottom Rollers: Lower rollers that bear the machine’s weight.
  
• Front Idler: Spring-loaded wheel that maintains track alignment.
  
• Track Adjuster: Hydraulic cylinder with grease fitting that controls idler position and track tension.
  

Terminology and Adjustment Components

• Track Sag: The vertical distance between the track and the top of the bottom roller when the machine is lifted.
  
• Grease Cylinder: Hydraulic adjuster filled with grease to push the idler forward and tighten the track.
  
• Relief Valve: A bleed screw or fitting that allows grease to escape, retracting the idler and loosening the track.
  
• Track Pitch: The distance between track links, used to measure wear and elongation.
  

Adjustment Procedure and Best Practices

1. Lift the machine using the boom and blade until the track is off the ground.
   
2. Measure track sag at the midpoint between the front idler and sprocket. Ideal sag is typically 10–20 mm for rubber tracks.
   
3. Locate the grease fitting on the track adjuster, usually behind a protective plate near the idler.
   
4. To tighten the track, pump grease into the fitting using a manual grease gun. Monitor sag as the idler moves forward.
   
5. To loosen the track, carefully open the relief valve and allow grease to escape. The idler will retract under spring pressure.
   
6. Recheck sag after lowering the machine and driving forward and backward to settle the track.
   

A contractor in British Columbia reported that his ViO20 kept throwing tracks during cold mornings. After inspecting the adjuster, he found the grease had hardened, preventing proper tension. Flushing the cylinder and using low-temperature grease resolved the issue.
Common Mistakes and Troubleshooting Tips

• Over-tightening can cause excessive wear on rollers and increase fuel consumption.
  
• Under-tightening leads to track derailment, especially during turns or on slopes.
  
• Grease contamination may clog the adjuster. Use clean, high-pressure grease and inspect seals regularly.
  
• Relief valve damage can prevent proper loosening. Replace worn fittings and avoid overtightening.
  

Preventive Maintenance Recommendations

• Check track tension weekly, especially in rental or high-cycle environments.
  
• Inspect grease fitting and relief valve for leaks or corrosion.
  
• Clean track frame and rollers to prevent debris buildup that affects tension.
  
• Monitor track pitch to detect elongation and plan for replacement.
  
• Use manufacturer-recommended grease with appropriate viscosity for climate conditions.
  

Conclusion
Track adjustment on the Yanmar ViO20 is a critical maintenance task that directly affects machine performance and undercarriage life. By following proper procedures, monitoring sag, and maintaining clean hydraulic components, operators can ensure reliable travel and reduce downtime. Whether in landscaping or trenching, a well-tensioned track keeps the ViO20 moving efficiently and safely.