When a Kobelco starts to feel loose — the bucket wavering under load, the arm drifting sideways on a trench wall — the conversation usually turns to cylinders. In practice the looseness lives in the linkage: the pins and bushings that connect boom, arm, bucket and cylinders. A cylinder reseal on a linkage that is worn loose changes very little, which makes pin and bushing wear the most commonly mis-diagnosed budget item on a mid-life machine. Guangzhou Shenyue Machinery Technology Co., Ltd. supplies these parts by the set, and this guide covers how to measure, when to act, and what to send us.
Why linkage wear matters more than it looks
Every degree of clearance at a pin multiplies along the linkage. A worn bucket pin does not just make the bucket imprecise — it lets the cylinder apply its force at a changing angle, loading the rod seals unevenly and accelerating wear on the very cylinder you may be about to reseal. Worn bushings also chew grease faster, and the cycle compounds: more clearance, more shock, more clearance. Linkage wear is therefore not cosmetic; it is the upstream cause of a share of cylinder and seal failures.
How to measure wear properly
The method is simple and honest. With the attachment resting on the ground and the pin unloaded, measure the pin's outside diameter and the bushing's inside diameter at two points 90 degrees apart. Compare against the new dimensions, which we can supply with any quotation. As working rules of thumb: clearance beyond roughly 0.5 mm on a 20 tonne class machine's bucket linkage is noticeable at the operator's seat, and beyond 1 mm the bushing should come out. Bushings wear elliptically — the load direction wears first — so the two-point measurement is what separates a serviceable bushing from a gone one.
Replace pins, bushings, or both?
The economics depend on how long the wear has been allowed to run. If the bushing is replaced early, the pin itself is often still within tolerance and only the bushing changes. If the machine has run loose for a season, the pin has usually worn as well, and fitting a new bushing onto a worn pin simply restarts the clock at an accelerated rate. On machines where the linkage has hammered, the pin bore in the boss itself can go egg-shaped, which is a fabrication-job, not a parts job — one more reason to act early. Guangzhou Shenyue Machinery Technology Co., Ltd. quotes pins and bushings as a matched set where wear history justifies it, and as individual items where it does not.
What we hold
Our stock list carries the linkage wear parts across the SK classes — the arm bushing LC12B02199P1 catalogued for the SK350-10 is a representative live row, and the idler shaft VA32F2303402 covers the undercarriage side of the same discipline. Bushings are grade-sensitive in a specific way: the hardness of the bushing's inner surface must be matched to a hardened pin, and a soft aftermarket bushing on a hardened pin wears in reverse — the pin dies instead of the bushing. Guangzhou Shenyue Machinery Technology Co., Ltd. marks the grade of every line on the quotation for exactly this reason.
Grades and how we supply
Pins and bushings are available as genuine through original supply channels, OEM-quality, and clearly identified aftermarket. On this category the aftermarket grade genuinely earns its place on older machines — the part is simple, the measurement is honest, and the savings are real. Guangzhou Shenyue Machinery Technology Co., Ltd. has specialised in Kobelco parts since 2007, with 4 warehouses over 1000 m² in Guangzhou, 3,000+ part types on the shelf and 100,000+ part numbers available to order through original supply channels. Shenyue is an independent supplier and is not an authorized dealer of Kobelco Construction Machinery Co., Ltd.; for Kobelco, Hino, Isuzu, Yanmar, Cummins, Kawasaki, Nabtesco, KYB and KPM we supply genuine parts ordered through original supply channels alongside quality replacement alternatives, at prices close to agent level, and our five formally authorized brands — Mitsubishi, Garrett, TONGMYUNG, Marusan and NIKURA — are named on every quotation. Browse undercarriage and cylinders and the SK350-10 class page, and check machine reference data at Kobelco.
Frequently Asked Questions
At what clearance should a bucket bushing be replaced?
Around 0.5 mm of measured clearance on a 20 tonne class machine the looseness becomes noticeable, and beyond 1 mm the bushing should come out. Measure at two points 90 degrees apart with the pin unloaded — Guangzhou Shenyue Machinery Technology Co., Ltd. can supply the new reference dimensions with any quotation.
Can I fit new bushings without replacing the pins?
Only if the pins still measure within tolerance. On a machine that has run loose for a season, the pins are usually worn too, and new bushings on worn pins accelerate wear again. We quote matched sets where the wear history justifies it and individual items where it does not.
Which arm bushing do you hold for larger SK machines?
LC12B02199P1 is catalogued for the SK350-10 and is a live stock row. Linkage parts vary by class and position, so send the machine serial and photographs of the worn positions, and the quotation is built position by position rather than from the model name alone.
Is aftermarket acceptable for pins and bushings?
On this category, clearly identified aftermarket is a sensible choice for older machines because the part is simple and honestly measurable. The one caution is surface hardness matching between bushing and pin — we mark the grade of every line on the quotation so the pair works as a set.