Replacing Pins and Bushings on a Kobelco Excavator

[MikePhua]

The Kobelco SK115SRDZ and Its Linkage Wear Points
The Kobelco SK115SRDZ is a compact tail-swing excavator designed for urban and utility work, combining maneuverability with full-size digging power. Like most machines in its class, it relies on a series of hardened steel pins and bushings to connect the bucket, stick, and linkage components. Over time, these wear points become loose, leading to slop in the bucket, reduced breakout force, and accelerated wear on hydraulic cylinders.
The most common wear zones include:

• Bucket-to-stick connection
  
• Bucket linkage and “H” bar assembly
  
• Boom-to-stick pivot
  
• Swing frame bushings
  

These components are subject to constant load cycling, abrasive soil contact, and hydraulic shock. Replacing them restores precision and protects the structural integrity of the excavator.
Terminology Notes

• Pin: A cylindrical steel shaft that connects two moving parts, often retained by clips or bolts.
  
• Bushing: A sleeve, usually made of hardened steel or bronze, that provides a wear surface between the pin and housing.
  
• H Bar: A linkage component shaped like an “H” that transfers motion from the bucket cylinder to the bucket.
  
• OEM (Original Equipment Manufacturer): Parts supplied by the machine’s manufacturer, typically more expensive but guaranteed to fit.
  

Sourcing Options and Cost Considerations
Operators often face a choice between OEM parts and aftermarket alternatives. Kobelco’s genuine pins and bushings are known for quality but can be prohibitively expensive. In some cases, aftermarket suppliers offer replacements at one-third the cost, even with long-distance shipping.
Options include:

• Dealer-supplied OEM parts: Guaranteed fit, but high cost
  
• Aftermarket suppliers: Lower price, variable quality
  
• Custom fabrication by machine shops: Ideal for older machines or rare models
  

One operator in Australia sourced hardened steel bushings from a specialist supplier 800 km away. Despite the distance, the parts arrived with tight tolerances and excellent fit. Another technician in Canada relied on a local machine shop to measure and fabricate pins, saving time and avoiding import delays.
Recommendations for Accurate Fit and Longevity

• Measure worn components precisely using calipers and micrometers
  
• Document part numbers from online catalogs or dealer systems
  
• Use hardened steel or induction-hardened pins for durability
  
• Grease all joints thoroughly during installation
  
• Inspect bores for ovality or scoring before pressing in new bushings
  
• Consider line boring if housings are distorted
  

Some shops offer mobile service, sending technicians to measure and install pins onsite. This is especially useful for machines that cannot be transported easily or are mid-project.
Field Experience and Practical Advice
One operator noted that searching part numbers online often leads to better pricing than calling dealers directly. Another emphasized the importance of verifying supplier claims—some companies advertise “fits all machines” but fail to deliver precise dimensions.
In regions with strong industrial history, such as former paper mill towns, machine shops often retain the skills and equipment to fabricate pins and bushings quickly. These local resources can be more reliable than distant suppliers and offer installation support.
Conclusion
Replacing pins and bushings on a Kobelco excavator is a critical maintenance task that restores performance and prevents structural damage. While OEM parts offer guaranteed fit, aftermarket and custom options can deliver excellent results at lower cost. With accurate measurements, hardened materials, and proper installation, operators can extend the life of their machines and maintain tight, responsive linkage motion.