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Hitachi EX120-2 Excavator Overview
The Hitachi EX120-2 is a mid-size hydraulic excavator introduced in the early 1990s, designed for general construction, trenching, and light demolition. It features a 4-cylinder Isuzu diesel engine producing around 90 horsepower, a dig depth of over 18 feet, and an operating weight of approximately 27,000 pounds. The EX120-2 was part of Hitachi’s second-generation lineup, incorporating improved hydraulic efficiency and simplified maintenance access.
Hitachi Construction Machinery, founded in 1970, became a global leader in excavator design by the 1990s. The EX series was widely adopted across Asia, Europe, and North America, with tens of thousands of units sold. The EX120-2 remains popular among owner-operators and small contractors due to its reliability and mechanical simplicity.
Boom Compatibility Between EX100 and EX120-2
The EX100 is a slightly smaller predecessor to the EX120 series, sharing many design elements but differing in structural dimensions and hydraulic flow. While both machines use similar boom architecture—single-piece welded steel with internal reinforcement—the mounting points, pin diameters, and hydraulic port locations may vary.
Key considerations when evaluating boom compatibility:
In one case, a Connecticut-based welder rebuilding his EX120-2 discovered severe wear on the main boom pin. While searching for a replacement, he found a clean EX100 boom at a salvage yard. Before purchasing, he measured the pin diameter and bracket spacing, finding them close but not identical. With minor machining and bushing adjustment, the boom was successfully installed and performed well for light-duty work.
However, he noted that the EX100 boom had slightly less reach and required custom hydraulic hose routing. For heavy lifting or precision grading, the mismatch could have introduced performance limitations.
Recommendations for Owners
While the EX100 boom may fit the EX120-2 with modification, it is not a direct swap. Compatibility depends on precise measurements and willingness to adapt mounting and hydraulic connections. For operators with fabrication skills and access to machining tools, this can be a cost-effective solution. However, for critical lifting or resale value, sourcing the correct EX120-2 boom remains the safest choice.
The Hitachi EX120-2 is a mid-size hydraulic excavator introduced in the early 1990s, designed for general construction, trenching, and light demolition. It features a 4-cylinder Isuzu diesel engine producing around 90 horsepower, a dig depth of over 18 feet, and an operating weight of approximately 27,000 pounds. The EX120-2 was part of Hitachi’s second-generation lineup, incorporating improved hydraulic efficiency and simplified maintenance access.
Hitachi Construction Machinery, founded in 1970, became a global leader in excavator design by the 1990s. The EX series was widely adopted across Asia, Europe, and North America, with tens of thousands of units sold. The EX120-2 remains popular among owner-operators and small contractors due to its reliability and mechanical simplicity.
Boom Compatibility Between EX100 and EX120-2
The EX100 is a slightly smaller predecessor to the EX120 series, sharing many design elements but differing in structural dimensions and hydraulic flow. While both machines use similar boom architecture—single-piece welded steel with internal reinforcement—the mounting points, pin diameters, and hydraulic port locations may vary.
Key considerations when evaluating boom compatibility:
- Pin Diameter and Spacing: The main boom pin (closest to the cab) must match in diameter and center-to-center spacing. Even a few millimeters of difference can cause misalignment or stress fractures.
- Hydraulic Port Location: The boom’s hydraulic lines must align with the stick and cylinder ports. If the EX100 boom has different routing, custom hoses or adapters may be required.
- Weight and Balance: The EX100 boom may be lighter or shorter, affecting reach and lifting capacity. This could alter the machine’s center of gravity and reduce stability during heavy lifts.
- Mounting Brackets: The boom base must seat properly on the upper frame. If the EX100 boom uses a different bracket style, welding or machining may be necessary.
- Boom: The primary lifting arm of an excavator, connected to the stick and bucket.
- Pin Diameter: The thickness of the steel pin used to connect hydraulic components.
- Hydraulic Port: The entry or exit point for hydraulic fluid in cylinders or hoses.
In one case, a Connecticut-based welder rebuilding his EX120-2 discovered severe wear on the main boom pin. While searching for a replacement, he found a clean EX100 boom at a salvage yard. Before purchasing, he measured the pin diameter and bracket spacing, finding them close but not identical. With minor machining and bushing adjustment, the boom was successfully installed and performed well for light-duty work.
However, he noted that the EX100 boom had slightly less reach and required custom hydraulic hose routing. For heavy lifting or precision grading, the mismatch could have introduced performance limitations.
Recommendations for Owners
- Measure Before Buying: Use calipers and tape to measure pin diameters, bracket spacing, and boom length.
- Consult Parts Manuals: Compare part numbers and diagrams from both models to identify structural differences.
- Use OEM Bushings or Machine Custom Sleeves: If pin diameters differ, install bushings or machine sleeves to fit.
- Test Hydraulic Flow: After installation, verify that cylinders operate smoothly and without binding.
- Document Modifications: Keep records of changes for future maintenance or resale.
While the EX100 boom may fit the EX120-2 with modification, it is not a direct swap. Compatibility depends on precise measurements and willingness to adapt mounting and hydraulic connections. For operators with fabrication skills and access to machining tools, this can be a cost-effective solution. However, for critical lifting or resale value, sourcing the correct EX120-2 boom remains the safest choice.
