31Y1-21200: Adjust Boom Hydraulic Cylinder Seal Kit for Hyundai Excavator R140LC-7A
31Y1-21200 Adjust Boom Cylinder Seal Kit — Product Overview
The 31Y1-21200 Adjust Boom Cylinder Seal Kit is a precision aftermarket replacement for Hyundai R210LC-9, R220LC-9S, R220LC-9SH, R210NLC-9, and R220LC-9A excavators. Designed for the left-hand adjust boom cylinder with 75mm rod and 105mm bore dimensions, this kit is manufactured to Hyundai OEM specifications using premium sealing materials etc.
The adjust boom cylinder is a specialized hydraulic component found on mid-to-large Hyundai excavators. It controls the angular positioning of the boom relative to the machine’s upper structure — enabling the operator to fine-tune the boom’s working angle for optimal digging geometry in varied terrain. Unlike the main boom cylinder that handles vertical lift, the adjust cylinder manages precise angular positioning under continuous vibration and side loads.
Seal failure in the adjust boom cylinder causes angle drift (the boom slowly shifts out of its set working position), reduced digging precision, and hydraulic oil leakage. The 31Y1-21200 kit uses polyurethane rod seals and NBR static seals etc for reliable angular positioning control. DJF Seals supplies this kit at factory-direct wholesale pricing.
Technical Specifications
| Parameter | Specification |
| OEM Part Number | 31Y1-21200 |
| Compatible Brand | Hyundai |
| Cylinder Application | Adjust Boom Cylinder (LH) |
| Rod Diameter | 75 mm |
| Bore Diameter | 105 mm |
| Applicable Models | R210LC-9, R220LC-9S, R220LC-9SH, R210NLC-9, R220LC-9A |
| Material | Polyurethane, NBR, PTFE etc |
| Condition | New, Aftermarket Replacement |
| Business Type | Factory Direct Wholesale |
Compatible Models
- Hyundai R210LC-9 — Adjust Boom Cylinder (LH)
- Hyundai R220LC-9S / R220LC-9SH — Adjust Boom Cylinder (LH)
- Hyundai R210NLC-9 — Adjust Boom Cylinder (LH)
- Hyundai R220LC-9A — Adjust Boom Cylinder (LH)
Key Features & Benefits
- Angular Precision Sealing — 75mm rod × 105mm bore. PU rod seal maintains precise boom angle positioning under continuous vibration and side loads during excavation.
- 5-Model Coverage — One kit fits Hyundai R210LC-9, R220LC-9S, R220LC-9SH, R210NLC-9, and R220LC-9A adjust boom cylinders.
- Anti-Drift Performance — Engineered to hold angular position under sustained load, preventing the boom from drifting out of its set working angle during extended dig cycles.
- Complete Reseal Kit — Rod seal, piston seal, wiper, O-rings, and backup rings included for a full adjust boom cylinder rebuild.
- Factory-Direct Wholesale — Competitive pricing with flexible MOQ. Sample orders accepted for quality verification.