Komatsu PC78US Used Excavator Buyer Guide

The Komatsu PC78US is a useful choice for buyers who need more working capability than a mini excavator but still operate on jobsites where rear clearance is limited. Its short-tail design makes the model especially relevant for urban construction, utilities, road work, trenching and other jobs where a conventional excavator of similar weight may require more space.

For a used buyer, however, the PC78US name covers several generations. Machines such as the PC78US-6, PC78US-8, PC78US-10 and PC78US-11 differ in engines, controls, operating weight and other specifications. This guide explains how to decide whether this approximately 7- to 8-ton class machine suits your work, which version you may encounter, and what should be checked before purchasing an individual unit from Japan.

Why Choose a PC78US Instead of a Smaller Excavator?

The PC78US occupies an important position between compact mini excavators and larger conventional crawler excavators.

Komatsu describes the PC78US-11 as a small excavator designed for underground utility and general construction work in urban environments. Its short-tail layout is intended to improve maneuverability in confined areas. Earlier PC78US generations were developed around the same basic idea: useful excavating performance in a machine that needs less rear working space.

This makes the PC78US worth considering when your work includes:

• Utility installation and repair
• Water and drainage trenches
• Road construction and maintenance
• Urban and residential construction
• Foundation excavation
• Site preparation and grading
• Loading smaller trucks
• Backfilling with a blade-equipped machine
• Attachment work where the machine has the correct hydraulic circuit

The main reason to move up from a smaller PC30MR or PC50MR is not simply to own a larger excavator. The PC78US class becomes more relevant when the required digging depth, reach, stability and daily production begin to exceed what a smaller mini excavator can comfortably provide.

What Does “US” Mean for the Buyer?

The defining characteristic of the PC78US family is its short-tail concept. Komatsu developed the PC78US as a short-tail swing hydraulic excavator, allowing the rear of the upper structure to remain closer to the machine's track footprint during rotation than on many conventional excavators.

For example, Komatsu lists a 1,240 mm tail swing radius for the PC78US-8. The current PC78US-11 continues the compact concept and is promoted specifically for restricted working areas.

This feature matters on sites where an excavator works:

• Beside active traffic
• Between buildings
• Along narrow property boundaries
• Near walls and structures
• Inside developed urban sites
• Where people or other equipment operate close to the machine

A short tail does not eliminate the need for safe swing clearance. The boom, arm, attachment and counterweight still move through working areas. Buyers should treat compact dimensions as a jobsite advantage, not as permission to operate without adequate safety space.

PC78US Generations: Do Not Compare Them as One Specification

A buyer searching Japanese used machinery may encounter several PC78US generations.

Komatsu's own technical history states that the PC78US-6 was introduced in August 2001 as a new-generation short-tail hydraulic excavator. Later generations include the PC78US-8, PC78US-10 and PC78US-11.

The PC78US-8 remains particularly relevant to used-equipment buyers. Komatsu still lists the model in its international crawler excavator information, and PC78US-8 machines also appear in the Japanese used market. Later versions increased engine output and introduced updated emissions, hydraulic and electronic systems.

Specifications vary by model year, series, market and configuration. Exact specifications should be confirmed for each individual machine.

Official Specification Examples

These figures show why “PC78US” should not be treated as one fixed specification. Even within one generation, shoe width, arm length, bucket, blade and other equipment can change operating weight and working range.

The PC78US-8 Is Especially Relevant in the Used Market

For buyers sourcing machinery from Japan, the PC78US-8 deserves particular attention because it represents a generation old enough to appear regularly as used equipment while still offering several features associated with more modern excavators.

Komatsu's official PC78US-8 documentation identifies a Komatsu SAA4D95LE-5 turbocharged and aftercooled diesel engine with 41 kW / 55 HP net output. The machine uses electronically controlled engine and hydraulic systems and offers multiple working modes.

Komatsu's Japanese archived product information gives a representative Japanese-market PC78US-8 machine mass of 7,290 kg, 0.28 m³ bucket capacity and 41.0 kW rated output. International specifications show wider ranges because configurations and market requirements differ.

This is a good example of why overseas buyers should obtain the specification of the actual machine being offered rather than copying a number from a catalog for another country.

How Much Work Can a PC78US Handle?

The PC78US is not simply a larger mini excavator. Its size gives it greater potential for trenching, digging, grading and material handling than smaller compact machines, while retaining a design focused on confined work.

As one reference point, the PC78US-11 with the specified 2,250 mm arm has a maximum digging depth of 4,660 mm and maximum digging reach of 6,920 mm in Komatsu's official specification.

Those values should not be transferred directly to an older PC78US or a machine with a different arm.

Before choosing this class, identify what your normal jobs actually require:

Attachment Capability Can Change the Value of a Used Machine

A PC78US may be used with equipment other than a standard digging bucket, but attachment capability must be checked on the individual machine.

The newer PC78US-11 provides one-way and two-way auxiliary hydraulic capability and programmable attachment settings. Komatsu specifies different hydraulic flow values depending on circuit operation. This supports applications involving compatible attachments such as breakers or crushers.

Older PC78US machines may have different piping, control systems or optional equipment.

Before paying more for a machine because it is advertised as “breaker piping” or “multi piping,” verify:

• Which hydraulic lines are actually installed
• Whether flow is one-way, two-way or selectable
• Whether the machine has attachment controls in the cab
• The required pressure and flow of your intended attachment
• Whether a quick coupler is included
• What bucket or attachment is included in the sale

Visible piping does not by itself prove that every hydraulic attachment will be compatible.

A PC78US Used Inspection Should Focus on Its Work History

An approximately 8-ton excavator can accumulate significant structural, hydraulic and undercarriage wear. Inspection should therefore try to identify not only what is worn but also how the machine may have been used.

Engine and Cooling System

Where practical, evaluate a cold start. Look for difficult starting, abnormal smoke, unstable idle, unusual sounds and visible leakage.

Inspect the radiator and cooling areas for contamination or damage. A machine that has worked in dusty demolition, recycling or earthmoving conditions may require different attention from one that spent most of its life on cleaner utility jobs.

Hydraulic Pump, Cylinders and Hoses

Operate the boom, arm, bucket, swing and blade through normal movements. Watch for slow response, irregular operation or unusual noise.

Inspect cylinder rods for damage and check around seals, hoses, pipes and joints for leakage.

On machines previously used extensively with a hydraulic breaker, pay particular attention to hydraulic condition and working-equipment wear.

Boom, Arm and Attachment Mounting Area

Check the boom and arm for cracks, deformation, reinforcement or welding. Inspect around cylinder mounting points and pin bosses.

A repaired area is not automatically unacceptable. Buyers should determine what was repaired, whether alignment remains correct and whether the repair shows signs of further cracking.

Pins and Bushings

Excessive play can develop at the bucket linkage, arm, boom and other pivot points. Some movement is normal on a used excavator, but significant looseness may mean future parts and labor costs.

Bucket movement under load can make wear easier to identify than appearance alone.

Undercarriage

Tracks, rollers, sprockets, idlers and related components deserve careful attention because replacing several undercarriage components can materially change the total cost of ownership.

Check both sides rather than judging from one photograph. Uneven wear may be as significant as the total amount of wear.

Blade and Lower Frame

PC78US machines may perform backfilling and grading as part of normal site work. Inspect the blade edge, blade cylinder and mounting structure.

Also look underneath the machine for impact damage, heavy corrosion or evidence of repeated operation over rough material.

Operating Hours: Useful, but Not the Final Answer

Operating hours become tempting as a simple way to rank used excavators. They should instead be used as one part of a condition assessment.

Two machines showing 6,000 hours may have experienced very different lives. One might have received routine maintenance and spent its time on general excavation. Another might have worked with a breaker in severe conditions.

Compare the displayed hours with:

• Maintenance information when available
• Undercarriage condition
• Hydraulic performance
• Pin and bushing wear
• Cab and control wear
• Bucket and attachment condition
• Engine behavior
• Visible structural repairs

A low-hour number should not override evidence of poor condition.

Lifting Capacity Is Not One Number

Buyers planning to lift pipes, construction materials or other loads should use the correct lifting chart for the exact machine.

Komatsu's official PC78US documentation shows that rated lifting values change according to lifting radius, load height, arm length, bucket configuration and machine position. On the PC78US-8, Komatsu also distinguishes between loads limited by hydraulic capacity and those limited by stability.

Therefore, quoting one “maximum lifting capacity” without operating conditions can be misleading.

If lifting is part of the planned job, confirm the full model, arm, shoe width, blade position and manufacturer's appropriate load chart. Local workplace and lifting regulations should also be checked before operation.

PC50MR or PC78US: When Does Moving Up Make Sense?

The PC50MR and PC78US can both appeal to buyers who want compact construction equipment, but they solve different capacity requirements.

Moving up to a PC78US makes sense only if the extra capability will actually be used. A heavier excavator can increase transport, fuel and undercarriage costs, so a smaller machine may remain the better tool for lighter jobs.

Shipping a PC78US from Japan Requires More Planning

The PC78US is still compact by excavator standards, but international shipping requires more planning than with a small mini excavator.

For the PC78US-11, Komatsu lists operating weights between 7,910 and 8,250 kg depending on track configuration. PC78US-8 official specifications also show a configuration-dependent range. Shipping weight may differ from operating weight according to fuel, bucket, attachments and preparation for transport.

Before calculating freight, confirm:

1. The complete model designation and serial number.
2. Actual overall length, width and height.
3. Actual transport weight.
4. Bucket and attachment dimensions.
5. Whether any components will be removed for transport.
6. The destination port.
7. Available shipping-line service.
8. Loading and unloading requirements at the destination.

Container, RORO, flat rack or other cargo arrangements may be considered depending on the individual machine, destination, port, shipping line and current service conditions. Do not assume that every PC78US can use the same shipping method.

Your Pre-Purchase PC78US Checklist

1. Identify the generation. Confirm PC78US-6, PC78US-8, PC78US-10, PC78US-11 or other exact designation.
2. Verify the serial number. Use the machine plate rather than relying only on advertisement text.
3. Confirm operating hours. Then compare them with actual component wear.
4. Check the engine and hydraulics. Look beyond cosmetic appearance.
5. Inspect the undercarriage. Consider remaining track, sprocket and roller life.
6. Inspect pins and working equipment. Look for excessive movement, cracks and repairs.
7. Confirm attachments and piping. Know exactly what is included.
8. Verify dimensions and weight. Use the actual configuration for shipping planning.
9. Compare it with your work. Digging capability is useful only if the machine fits the jobsite and transport system.

Buying a Used PC78US from Japan

The Japanese used market can contain several PC78US generations with different hours, attachments and histories. This makes condition comparison more important than selecting by generation alone.

You can check current Japanese used machinery available at EVERYCAR.jp. Inventory changes regularly, so a specific PC78US model or configuration may not always be available.

For more information about choosing excavators and other Japanese used equipment, visit the Japanese Used Machinery & Heavy Equipment Guide | 100 Articles.

Is the Komatsu PC78US the Right Excavator for Your Work?

The PC78US makes the strongest case when a buyer needs more capability than a small mini excavator but cannot give up the advantages of a compact rear swing. Utility contractors, road crews, builders and other operators working in developed or restricted sites are the most obvious candidates.

Before purchasing, identify the exact generation and specification. Then judge the engine, hydraulics, undercarriage, working equipment and attachments as one complete machine. Finally, compare its verified digging range, transport requirements and condition against the work it will actually perform.

If you are looking for a Komatsu excavator or other used machinery from Japan, you can contact EVERY with your preferred manufacturer, model, size, budget and destination. Providing your intended application as well can help narrow the search to machinery that better matches your operating requirements.