Repair Link Kits Guide: Joining a Broken Track Chain

A repair link kit is the smallest part that rescues the largest problem. When a chain is broken - by a seized roller, a shock load, or a link that has worn through - the machine does not need a new undercarriage, it needs the chain joined again with a link that matches its pitch, its bushing diameter and its pin size. Get those three right and the repair is a morning's work; get them wrong and the joint fails under load and takes the surrounding links with it.

Last updated: October 6, 2026

This page collects what we publish about link kits: what a master link and a repair link actually are, how fitment is confirmed, what to expect when buying for a legacy machine, and where to buy in Canada. The whole range is in repair link kits.

What a link kit is, and when it is the right answer

A track chain is a sequence of links joined by pins and bushings. A master link is the factory joint that lets the chain be assembled and disassembled, and a repair link is a replacement for a section that has been damaged - usually one or two links plus their fasteners. A kit normally arrives as the link, the pins or bolts, and everything needed to close the joint.

The kit is the right answer when the chain has failed in one place and the rest of it is serviceable: a link cracked by impact, a seized roller that has worn through a link edge, or a joint that has opened up. It is the wrong answer when the chain as a whole is stretched beyond its wear limit, because a new link fitted into an elongated chain changes the pitch at that point and the chain will not run smoothly on the sprocket. The honest test is a chain wear measurement before ordering - if the chain is past its limit, the money belongs in a chain and sprocket, not in a link.

Confirming fitment

Four facts identify the right kit, and a supplier should be able to quote all four. The part number cross-referenced against the machine's model and serial number - which is what the Komatsu kit guidance is really about. The chain pitch, since the link has to sit at the same spacing as the rest of the chain. The bushing and pin diameters, including whether the joint is retained by bolts or by pins. And the link height and width, which have to match the chain's other links closely enough that the rollers and sprocket treat the joint as normal chain.

Two practical points belong in the same check. First, measure the chain, not just the broken link, because a chain stretched past its limit will not run true even with a perfect joint. Second, check that the kit is supplied with the fasteners - a link without the correct pins or bolts is not a repair, and reusing the old ones is how the joint opens again in service.

Buying for a legacy or mixed fleet

Link kits are the part where legacy machines bite most, because the older a chain is, the less likely its dimensions are obvious from the machine's badge. Four items belong in writing: the part-number cross-reference for the model and serial number; the chain pitch, bushing and pin dimensions as supplied; the warranty terms as a period plus an operating-hours cap with freight responsibility named; and the stock position with a delivery date, because a machine with an open chain is not working at all.

Where a fleet spans several brands, it is worth keeping a record of which kit fits which chain rather than which machine - the same link often serves several models within a generation, and the number is what makes a repeat order a one-minute job. The buying logic is the same whether the machine is a bulldozer or an excavator, which is why the best Komatsu kit for bulldozer tracks and finding a kit for a PC300 excavator end up at the same questions.

Fitting a link kit

The sequence is short but unforgiving. Release the track tension before anything is undone, so the chain is slack and the joint is not under load. Remove the failed link and clean the two links it will join, because grit in the joint prevents the faces seating. Fit the new link with its fasteners, torque them to the specification, then re-tension the track and re-check the joint after the machine has run for a few hours.

Two safety points are worth stating plainly. The tensioner holds grease under pressure, so keep your body out of the line of the valve outlet when releasing tension. And a chain under load can move suddenly - support the machine properly, and work with the machine isolated rather than relying on the machine holding itself.

Master link and repair link are not the same part

The two are related and regularly confused. A master link is the joint the chain was assembled with at the factory: it is designed to be opened so the chain can be split, and on many machines it is also the joint used to shorten or adjust the chain as it wears. A repair link replaces a damaged section - usually one or two links - and is supplied as a kit with its own pins or bolts and retaining hardware.

Why the distinction matters when buying: a chain that has merely been opened needs the correct master link for its pitch and bushing size, while a chain that has lost a link to damage needs a repair kit sized to the same dimensions. Supplying one when the other is required is the most common wrong-part order in this category, and the failure mode is the same either way - a joint that does not seat properly and opens again under load, usually at the worst moment.

There is also a third case worth recognising: a chain that has failed at a seized roller or a worn sprocket rather than through any fault of its own. Repairing the chain without addressing the cause produces a machine that breaks the same joint again within weeks. That is why the link kit is the last step in the repair rather than the first.

How a joint fails, and what the failure tells you

Three patterns cover most joint failures. Wear at the pin or bolt - visible as a polished flat or a loose fit - usually means the hardware was reused or the joint was not torqued to specification. A joint that opens under load points at fasteners of the wrong grade, or at a chain that is running at the wrong tension and putting shock loads through the joint every revolution. And a cracked link is an impact failure: something in the track - a rock, a seized roller, a hooked sprocket tooth - has applied a load the link was not designed for.

Reading the failure before ordering saves the repair. If the joint opened rather than wore, the replacement kit needs the correct fasteners and the machine needs its tension checked; if the link cracked, the undercarriage needs inspecting for what caused it. A new link fitted into an assembly that is still causing the problem is a repair that will be repeated, and repeat failures are almost always cheaper to prevent than to fix.

The rest of this cluster

By machine: Caterpillar excavators, Caterpillar track loaders, whether aftermarket kits suit Cat machines, Komatsu PC200, heavy-duty kits for Cat D8 machines and Kubota excavators. By application: forestry, agricultural machinery and rental fleets. Buying and evaluation: OEM replacement parts for link kits, what high-performance kits bring to construction equipment and evaluating a supplier. Wider picture: excavator undercarriage parts and the rubber tracks guide.

FAQs

What is a repair link kit?

It is a replacement link - with its pins or bolts - used to join a track chain after a section has been damaged, so the chain can be returned to service without replacing the whole assembly.

How do I know which kit fits my chain?

By the part number cross-referenced against the machine's model and serial number, then confirmed against the chain pitch, the bushing and pin diameters, and the link height and width.

Should I repair the chain or replace it?

Repair if one link has failed and the chain is otherwise within its wear limit. If the chain is stretched past that limit, a new link changes the pitch at the joint, and the money belongs in a chain and sprocket instead.

Does the kit include the fasteners?

A complete kit does. If it does not, source the correct pins or bolts with it - reusing the old fasteners is how a repaired joint opens up again in service.

Can a link kit be fitted on site?

Yes, with the track tension released and the machine properly supported. Release the tension, clean the joint faces, fit the link, torque the fasteners, then re-tension and re-check after a few hours of work.