Lifting the Load: Counterweight Removal and Thread Specifications on Kobelco ED150SRLC and SK135-1E Excavators

[MikePhua]

Excavators like the Kobelco ED150SRLC and its mechanical sibling, the SK135-1E, are marvels of hydraulic and structural engineering. Built for precision in tight spaces, they feature a short tail swing and excellent balance. One of the critical design elements enabling that balance is the counterweight—a dense steel mass bolted to the rear of the machine. When it’s time to remove that counterweight for transport, repair, or access to internal components, understanding the correct thread size and lifting procedure becomes essential.
Why Counterweight Removal Matters
Counterweights serve one clear function: they balance the forward-heavy action of the boom and arm. However, when transporting an excavator on a lowboy trailer, weight restrictions often require the counterweight to be removed. In other cases, technicians may need to remove it to access rear-mounted hydraulic components or cooling systems.
But detaching this mass—often weighing over 2,000 lbs (900+ kg)—isn’t as simple as undoing a few bolts. Safety is paramount, and using the correct lifting eyes, bolt threads, and torque procedures is critical.
Thread Size: Matching Lifting Eyes to OEM Specs
For Kobelco machines like the ED150SRLC and SK135-1E, the counterweight lifting points are threaded to accept a specific type of eye bolt. The correct thread size for these machines is typically M24 x 3.0 mm. This metric specification refers to:

• M24: The diameter of the bolt shaft is 24 millimeters.
  
• 3.0 mm: The pitch of the threads (distance between each thread).
  

Using the wrong size—especially American-standard bolts like 1-inch UNC—can result in poor thread engagement, stripping, or even a catastrophic load drop. Manufacturers recommend grade 8.8 or 10.9 lifting eyes for safe counterweight removal. In practice, this means using forged, stamped eye bolts rated for vertical lifting.
An anecdote from a forestry operator in British Columbia described how a rushed job using an SAE-threaded lifting eye nearly caused a counterweight to drop onto a mechanic’s foot. The team caught the mismatched thread just in time, saving both the machine and a limb.
How to Safely Remove a Counterweight

1. Check the Service Manual
   Kobelco service guides typically provide a diagram showing lifting eye locations and thread specs. They also include torque values for reinstalling bolts—often in the range of 300–400 Nm for M24 fasteners.
   
2. Use Proper Rigging Equipment
   Always use certified lifting straps, shackles, and a hoist with enough capacity (at least 2 tons for these machines). Chain slings rated for heavy lifting should be checked for wear and properly secured.
   
3. Support the Load Fully Before Unbolting
   Position the lifting device so it takes the full weight before loosening any bolts. Failure to do so can cause the counterweight to shift suddenly as bolts are released.
   
4. Label Bolts and Thread Locations
   Because some bolt holes may vary slightly in depth or pitch, it’s helpful to mark their locations for reassembly.
   

OEM Comparisons and Regional Variations
The Kobelco SK135SR series and ED150SRLC share many components. Built primarily for North American markets, these machines often carry hybrid labeling: metric threads on an otherwise “standard” frame. This has tripped up more than one technician expecting inch-based measurements.
Interestingly, similar models sold in Europe or Asia may have slight variations in mounting hole tolerances or thread coatings due to regional manufacturing standards or corrosion requirements.
News Flash: Manufacturer Oversights and Industry Lessons
In 2020, a mid-sized equipment dealer in Australia issued a service advisory after discovering a batch of aftermarket lifting eyes had shallow threads, leading to partial engagement and near failures. The warning reminded owners to always verify lifting accessories with digital calipers before use, especially when ordering from third-party suppliers.
Transport and Legal Considerations
In many U.S. states, DOT weight and height restrictions for oversized loads make counterweight removal non-negotiable. A fully outfitted ED150SRLC might weigh 35,000 lbs, but removing the 2,200-lb counterweight brings it under axle-weight limits, eliminating the need for an escort vehicle.
Conclusion
Removing a counterweight on a Kobelco ED150SRLC or SK135-1E excavator is not just a matter of convenience—it's a vital operation that requires precision, proper tools, and a deep respect for safety standards. Knowing the correct thread size, such as M24 x 3.0 mm, and using properly rated lifting equipment can prevent costly damage and injury. Whether you're preparing for transport or accessing internal components, lifting the load starts with understanding how it's attached—and how to remove it the right way.