707-01-0A531 Komatsu PC800SE Arm Cylinder Aftermarket

Product Overview

SEIGO’s aftermarket arm cylinder, part number 707-01-0A531, is a direct drop-in replacement for the Komatsu PC800SE, PC800 and PC750SE hydraulic excavators — large 75 to 80 tonne class machines used in quarrying, mining and heavy construction. Komatsu catalogues this part as the Arm Cylinder for the 7.1 metre boom configuration. Also called the stick cylinder or dipper cylinder, it controls the crowd and dig motion of the arm, and works with a 185 mm bore and 120 mm rod.

This single part number covers a wide span of the PC750SE / PC800SE family across the dash-6 and dash-7 generations. Depending on machine and serial number it is fitted to the PC750SE-7, PC800-6, PC800-7, PC800SE-6, PC800SE-7 and their regional variants. Because the number spans several machines and build years, confirm your machine model and serial number when ordering — SEIGO manufactures the correct specification for each variant.

The arm cylinder on an excavator of this size sustains the primary breakout and crowd force on every dig cycle, making it one of the highest-loaded actuators on the machine. Its failure pattern is driven by that sustained load combined with the abrasive, high-contamination environment at the working face: rod chrome scoring from grit, primary rod seal leakage once the chrome is compromised, and internal bypass from piston seal wear. Rod chrome adhesion and seal specification are therefore the two variables that most directly set service life on this position.

SEIGO manufactures the 707-01-0A531 to full OEM dimensional specification: a 42CrMo4 induction-hardened, hard-chrome-plated piston rod at 120 mm diameter, an ST52 seamless honed steel barrel machined to the 185 mm bore, and a genuine NOK (Japan) or Parker (USA) seal kit — the matching Komatsu seal kit for this cylinder is 707-99-68660. Every unit is pressure tested at 1.5× rated working pressure before shipment from our Guangdong factory and is backed by a 12-month or 2,000 operating-hour warranty. Standard lead time is approximately 30 days ex-works, with expedited production available for machine downtime.

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.

707-01-0A531 Machine Fitment & Serial Numbers

This arm cylinder is fitted across the PC750SE and PC800 / PC800SE family with the 7.1 m boom. The table below lists the applications and serial-number breakpoints as catalogued.

Fitment and serial breakpoints are compiled from Komatsu parts catalogue data for the arm cylinder (7.1 m boom). Confirm your full machine serial number before ordering, as boom length and build revision affect the correct cylinder. SEIGO supplies arm, boom and bucket cylinders across the PC750 / PC800 family.

Komatsu PC750 / PC800 Work Equipment Cylinder Reference

The PC750 / PC800 work equipment uses boom, arm and bucket cylinders. Part 707-01-0A531 is the arm cylinder. Related numbers within the family are listed below for cross-reference.

Related numbers are listed for cross-reference within the PC750 / PC800 family. The exact number for your machine depends on model, boom length and serial number. Confirm before ordering. SEIGO supplies boom, arm and bucket cylinders, and matching seal kits, for the full PC750 / PC800 range.

Why This Cylinder, Specifically

• Correct boom configuration, verified. This arm cylinder is catalogued for the 7.1 m boom across the PC750SE / PC800SE family. Because the family spans dash-6 and dash-7 generations and several regional variants, we confirm the exact specification against your serial number before quoting.
• Manufactured to OEM dimensions. 185 mm bore, 120 mm rod — built to reproduce the original crowd force and dig geometry exactly, with no change to breakout or reach.
• Built for sustained dig load. The arm cylinder carries the primary breakout force on every cycle. We specify 42CrMo4 induction-hardened, hard-chrome-plated rod dimensioned for that load, because the failure mode here is chrome scoring and seal wear, not rod bending.
• Matching seal kit available. The Komatsu seal kit for this cylinder is 707-99-68660 (code P-UB-14). We supply the complete cylinder, the seal kit alone, or individual rod, barrel, head and piston components — whichever your rebuild requires.
• Sub-component supply. For workshops rebuilding in-house, sub-component supply typically runs 40–60% of the cost of a complete replacement cylinder. On arm cylinders, rod and seal replacement is the most common single-item order. Send us your serial number and the component you need.
• Full traceability and testing. ISO 9001:2015 manufacturing, 100% pressure tested at 1.5× rated working pressure, shipped in an ISPM-15 fumigated export crate with material certificate and test record.

FAQ

Q1: Which machines does 707-01-0A531 fit?

A: It is the arm (stick) cylinder for the 7.1 m boom configuration across the Komatsu PC750SE and PC800 / PC800SE family — including PC800SE-6, PC800SE-7, PC800-6, PC800-7 and PC750SE-6/-7 and their regional variants. Because the number spans several machines and build years, confirm your model and serial number before ordering. Send us the serial number and we will verify the correct specification for your machine.

Q2: What are the bore and rod dimensions of 707-01-0A531?

A: The arm cylinder has a 185 mm bore and a 120 mm rod. The matching Komatsu seal kit is 707-99-68660 (seal code P-UB-14). If you are cross-referencing an unmarked cylinder, measure the barrel outside diameter and rod outside diameter and send us the figures — together with the pin-to-pin length, this is sufficient for us to confirm or manufacture a match.

Q3: Is 707-01-0A531 the same as 707-01-0A532?

A: They are companion numbers in the same arm cylinder group for this machine family. They share the same bore and rod dimensions. Depending on your machine model, boom length and build revision, one or the other applies. Send us your full machine serial number and we will confirm which number is correct for your unit before production.

Q4: What is the difference between the arm cylinder and the boom cylinder?

A: The arm (stick) cylinder, 707-01-0A531, controls the crowd and dig motion of the arm and has a 185 mm bore. The boom cylinders raise and lower the boom and are different parts with different dimensions. On the PC750/PC800 family the related numbers 707-01-0A510 and 707-01-0A511 belong to the same machine family. SEIGO supplies boom, arm and bucket cylinders for these machines — specify the position when you enquire.

Q5: Can I buy the seal kit, rod or barrel separately instead of a complete cylinder?

A: Yes. SEIGO manufactures the piston rod, honed barrel, cylinder head, piston and seal kit as individual items. The matching seal kit for this cylinder is 707-99-68660. For workshops with in-house honing and assembly capability, sub-component supply typically runs 40–60% of the cost of a complete replacement cylinder. Send us your machine serial number and the component you need for a quotation.

Q6: What is the lead time and how does it ship?

A: Standard production lead time is approximately 30 days ex-works Guangdong, China, with expedited production available for machine downtime. Each cylinder ships in an ISPM-15 fumigated wooden export crate, FOB Shenzhen, CIF or DDP. Sea freight is standard for planned replacements; air freight is available for urgent situations.