707-G1-05780 Komatsu PC2000-11 / PC2000-11R Arm (Stick) Cylinder Aftermarket Replacement

Product Overview

SEIGO’s aftermarket arm cylinder, part number 707-G1-05780, is a direct drop-in replacement for the Komatsu PC2000-11 and PC2000-11R hydraulic mining excavator — Komatsu’s current-generation 200-tonne class machine. The same cylinder appears in supplier catalogues under several names: arm cylinder, stick cylinder, and mid-arm cylinder all refer to this position. Komatsu also lists the alternate designation 707-H1-05780. It works as a set with the boom cylinder 707-G1-05760.

The arm cylinder generates the crowd force that fills the bucket, but on a production mining excavator that is only half of what it does. During truck loading the operator runs boom and arm together through most of the cycle — lifting out of the cut while curling the arm, then extending the arm while swinging to the truck. Komatsu specifically addressed this on the PC2000-11 with new EPC valves that optimise main valve spool control for increased speed during compound movement. Faster, more precisely controlled compound motion is good for cycle times, and it also means the arm cylinder spends more of each cycle under load while the entire front attachment is accelerating and decelerating in swing.

That matters because swing inertia on a 200-tonne machine does not travel in a straight line through the cylinder axis. A share of it arrives at the arm cylinder as side load on the rod, at the gland, in a plane the cylinder is not designed to carry. Combined with the arm cylinder’s naturally high stroke utilisation — it sweeps through most of its available travel on every dig, where a boom cylinder in bench-level truck loading often works within a narrower mid-stroke band — the arm position accumulates seal travel and gland wear faster than any other main work equipment cylinder on the machine. Rod straightness tolerance and gland bushing specification are therefore the two variables that decide service life here.

SEIGO manufactures the 707-G1-05780 to full OEM replacement specification: a 42CrMo4 induction-hardened, hard-chrome-plated piston rod rated to HRC 58–62, held to a straightness tolerance appropriate for a cylinder that carries side load in normal service; an ST52 seamless honed steel barrel with bore finish held to OEM tolerance across the full stroke; heavy-duty gland bushings rated for radial load; and a genuine NOK (Japan) or Parker (USA) seal kit specified for the PC2000-11’s high-pressure hydraulic circuit. Every unit is pressure tested at 1.5× rated working pressure before shipment from our Guangdong, China factory, and is backed by a 12-month or 2,000 operating-hour warranty. Standard lead time is 2–3 weeks ex-works, with a 5–7 day Rapid Production Track for mine-site emergency orders.

Generation warning: the PC2000-8 and PC2000-11 share no work equipment cylinder part numbers. The -8 uses the 707-E1 series; the -11 uses 707-G1. Fleets running both generations are the single most common source of wrong-part orders on this machine. Confirm your generation and full machine serial number before ordering — the cross-reference tables below cover both.

Product Specifications

* OEM part numbers, brand names and model designations are used for identification and cross-reference purposes only. SEIGO Machinery is an independent aftermarket manufacturer and is not affiliated with Komatsu Ltd.

Komatsu PC2000-11 Cylinder Cross-Reference

Left-hand and right-hand assembly designations are as published in the Komatsu parts catalogue. The PC2000-11 front attachment uses paired cylinders at the main work equipment positions — confirm quantity and side for your machine configuration. Cylinder specification should be confirmed against your full machine serial number before ordering, as regional emission variants, cold-area arrangements and attachment configuration can all affect the correct part number.

PC2000-8 vs PC2000-11 — Different Cylinder Series

The PC2000-8 and PC2000-11 are separate generations and share no work equipment cylinder part numbers. If you operate a PC2000-8, none of the 707-G1 numbers above apply:

If your fleet operates a mix of PC2000-8 and PC2000-11 machines, our engineering team can supply the correct cylinder for each unit based on serial number and attachment configuration, consolidated on a single purchase order.

Why This Cylinder, Specifically

• Correct generation, verified before quoting. The 707-E1 and 707-G1 series look similar on a purchase order and fit entirely different machines. We confirm the generation against your serial number before we send a price, not after you receive the crate.
• Built for side load, not just axial load. The arm cylinder on a swinging 200-tonne front attachment carries a component of swing inertia as radial load at the gland. We specify heavy-duty radial-rated gland bushings and hold rod straightness tighter than a purely axial application would require, because gland wear from side loading — not seal pressure failure — is the dominant wear mechanism at this position.
• High stroke utilisation, matched seal package. The arm cylinder sweeps through most of its available travel on every dig cycle. More seal travel per cycle means the seal package, not the barrel or rod, usually sets the first service interval. We fit NOK or Parker rather than a generic kit specifically because of the duty cycle here.
• Abrasive-environment rod finish. Coal, iron ore, copper and shot-rock loading all drive fine abrasive dust past the wiper on every stroke. Rod surface hardness and chrome adhesion determine how many hours pass before scoring begins — the single largest variable in service life on a mining excavator cylinder.
• Order the set, plan one shutdown. Boom and arm cylinders on the same machine accumulate hours together. If the arm cylinder has reached service limit, the boom cylinder 707-G1-05760 is usually close behind. We supply both on a single purchase order so the front attachment work happens in one planned shutdown rather than two unplanned ones.
• Rods and barrels supplied separately. For mine-site rebuild shops with honing and assembly capability, we supply the piston rod, honed barrel, cylinder head, piston, gland bushings and seal kit as individual items — typically 40–60% of the cost of a complete cylinder, and a fraction of the freight on a 200-tonne-class assembly.
• Emergency production track. Standard lead time is 2–3 weeks ex-works. When a shovel is down and the truck fleet is idle, our Rapid Production Track delivers in 5–7 working days subject to material availability.

FAQ

Q1: Is 707-G1-05780 the arm cylinder, the stick cylinder, or the mid-arm cylinder?

A: All three names refer to the same position and the same part. “Arm cylinder” is standard Komatsu terminology, “stick cylinder” is common in North American and Australian mining usage, and “mid-arm cylinder” appears in some supplier catalogues as a direct translation from Chinese-language documentation. If your parts system holds it under any of these names, 707-G1-05780 is the number to quote.

Q2: What is 707-H1-05780, and is it the same cylinder?

A: 707-H1-05780 appears in Komatsu catalogue listings alongside 707-G1-05780, following the same G1 / H1 pairing seen elsewhere in the PC2000-11 cylinder family — for example 707-G1-05760 and 707-H1-05760 at the boom position. We supply against either number. Send us your full machine serial number and we will confirm which specification applies to your machine before production begins.

Q3: Will a PC2000-8 arm cylinder fit my PC2000-11?

A: No. The two generations share no work equipment cylinder part numbers. The PC2000-8 uses the 707-E1 series — 707-E1-00640 for the backhoe arm and 707-E1-01850 for the front shovel arm — while the PC2000-11 uses 707-G1-05780. This is the most common ordering error we see on this machine, particularly in fleets that run both generations side by side. Always confirm the generation from the machine serial number rather than from a previous purchase order, since a purchase order for the -8 will look almost identical at a glance.

Q4: Does the arm cylinder wear faster than the boom cylinder on a PC2000-11?

A: In production truck loading, usually yes — but the failure mode is different rather than simply faster. Boom cylinders fail from sustained compressive load and rod chrome fatigue. Arm cylinders fail from a combination of high stroke utilisation and gland wear caused by side loading during compound movement, when boom and arm operate together while the front attachment is swinging. The practical consequence is that a leaking gland or visible rod scoring on the arm cylinder is not necessarily a sign of a defective unit; it is the expected wear pattern for the position, and it is why gland bushing specification matters more here than at the boom.

Q5: What are the warning signs of a failing PC2000-11 arm cylinder?

A: Watch for hydraulic oil weeping or streaming at the gland, particularly visible after the cylinder has been held extended; arm drift when the bucket is held out with the control lever in neutral and the engine running; slower or uneven crowd speed under load, most noticeable during compound movement rather than during isolated arm operation; and visible chrome scoring, pitting or delamination on the rod, especially in the band of the rod that sits at the gland during the loaded portion of the cycle. Any of these should trigger inspection. On a machine loading haul trucks continuously, a gland failure that goes unaddressed will contaminate the rest of the circuit.

Q6: Do you supply the boom cylinder as well?

A: Yes. The companion boom cylinder is 707-G1-05760. Because boom and arm cylinders on the same machine accumulate hours together, we recommend planning both replacements into the same shutdown where hour readings are similar. We can quote and ship both on a single purchase order, and can consolidate cylinders for mixed PC2000-8 and PC2000-11 fleets onto one shipment.

Q7: Can I buy the rod, barrel or seal kit separately instead of a complete cylinder?

A: Yes. SEIGO manufactures the piston rod, honed barrel, cylinder head, piston, gland bushings and seal kit as individual items and supplies them to hydraulic repair shops and mine-site rebuild facilities. For workshops with in-house honing and assembly capability, sub-component supply typically runs 40–60% of the cost of a complete replacement cylinder. On arm cylinders specifically, gland and bushing replacement is the most common single-item order, since gland wear from side loading usually reaches service limit while the barrel and rod remain serviceable. Send us your machine serial number and the component you need for a quotation.

Q8: What is the lead time and how does a 200-tonne class cylinder ship?

A: Standard production lead time is 2–3 weeks ex-works Guangdong, China. For mine-site emergency orders our Rapid Production Track can deliver in 5–7 working days subject to material availability. Given the physical size and weight of a 200-tonne-class arm cylinder, sea freight via FOB Shenzhen is the standard method for planned replacements, packed in an ISPM-15 fumigated wooden export crate. Air freight to major hub airports is available for urgent situations. We support FOB, CIF and DDP Incoterms.

Q9: Do you ship to mining operations globally?

A: Yes. We regularly supply 200-tonne-class mining excavator cylinders to open-pit operations across Indonesia (Kalimantan coal, Sulawesi and Papua nickel), Australia (Bowen Basin coal, Pilbara iron ore), Chile and Peru (copper), South Africa (Mpumalanga coal, Northern Cape iron ore), Mongolia, Canada, India and West Africa.