Products Description
FS450 Brush Cutter Gear Case Washer – Detailed Replacement Guide
Comprehensive Washer Reference for STIHL FS450 Gearbox Assembly
The gear case washers in the STIHL FS450 brushcutter are precision components that serve critical functions within the angle drive gearbox. Different washers are used for specific purposes: thrust washers transmit axial loads and maintain bearing preload, shim washers provide precise gear mesh adjustment, and guard washers protect the cutting attachment mounting area and shield the operator from debris. All washers must be inspected during gearbox service and replaced if worn, as they directly affect gear alignment, bearing life, and the safety of the cutting attachment mounting system.
Technical Profiles & Materials
Guard Washer (OEM 4119 717 2800)
This protective washer (also listed as 4119-717-2800) is a critical safety component mounted on the gear head output shaft. It forms part of the thrust plate assembly, with the guard washer fitted captive to the thrust plate body. The STIHL FS450 instruction manual explicitly warns: "Never use a thrust plate without the guard washer. Always replace a thrust plate if the guard washer is missing". Measuring approximately 60mm (2-3/8"), this washer provides a protective barrier between the cutting attachment and the gear housing, preventing debris ingress and protecting the operator from flung objects.
Thrust Washer (OEM 4128 713 1600)
This component serves as the main thrust washer for mounting cutting attachments to the splined gear head shaft. It features a convex side that must face upward during installation, as specified in the FS450 mounting procedure. Available as a genuine STIHL part, it is cross-referenced with aftermarket equivalents. This washer is essential for transmitting axial loads from the cutting attachment to the gearbox housing.
Shim Washers (20x28mm)
Three precision shim washers are used for bearing preload adjustment on the gear housing:
9296 021 1681: 20mm x 28mm x 0.1mm, DIN988 specification
9296 021 1685: 20mm x 28mm x 0.2mm
9296 021 1687: 20mm x 28mm x 0.3mm, DIN988 specification
Technical Specifications
| # | Component | OEM Part No. | Specification / Size | Function |
|---|---|---|---|---|
| 1 | Guard Washer | 4119 717 2800 | Approx. 60mm / 2-3/8" | Protective barrier for gear head |
| 2 | Thrust Washer | 4128 713 1600 | Spline shaft fitment | Cutting attachment load transfer |
| 3 | Shim Washer (0.1mm) | 9296 021 1681 | 20x28x0.1mm (DIN988) | Bearing preload adjustment |
| 4 | Shim Washer (0.2mm) | 9296 021 1685 | 20x28x0.2mm | Bearing preload adjustment |
| 5 | Shim Washer (0.3mm) | 9296 021 1687 | 20x28x0.3mm (DIN988) | Bearing preload adjustment |
| 6 | Guard Ring | 4128 717 2704 / 2706 | Multiple variants | Protective ring for cutting attachment |
| 7 | Rider Plate | 4119 713 3100 / 4116 713 3100 | Multiple variants | Cutting attachment mounting base |
Products Application
Gearbox Overhaul & Rebuild
When servicing the FS450 gear head, all washers should be inspected and replaced if worn or damaged. The guard washer (4119 717 2800) is a mandatory component of the thrust plate assembly and must always be present. Shim washers (9296 021 1681/1685/1687) allow precise adjustment of bearing preload during gearbox reassembly, ensuring correct gear mesh and extending bearing life.
Cutting Attachment Installation
The correct washer configuration is critical when mounting cutting attachments. For mowing applications, the guard ring must be fitted, and the thrust washer (4128 713 1600) must be installed with its convex side facing upward. Before mounting a circular saw blade, the guard washer must be removed and the guard ring for saw blades (with appropriate thrust plate) must be fitted.
Safety Compliance
The FS450 instruction manual explicitly requires the guard washer to be present on the thrust plate. Operating without this washer is strictly prohibited and may result in serious injury. The guard washer protects against foreign objects being flung back toward the operator.
Quality and Craftsmanship Details
Products Package
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FAQ
Q: How do I confirm which washers are used in my FS450 gearbox?
A:Refer to the FS450 parts diagram for your specific model variant (e.g., FS450Z). The main washers used are the guard washer (4119 717 2800), thrust washer (4128 713 1600), shim washers (9296 021 1681/1685/1687), and guard rings (4128 717 2704/2706).
Q: Can I operate the FS450 without the guard washer?
A: No. The STIHL FS450 instruction manual explicitly states: "Never use a thrust plate without the guard washer. Always replace a thrust plate if the guard washer is missing". Operating without this washer compromises operator safety.
Q: What is the correct orientation for the thrust washer (4128 713 1600)?
A: The thrust washer must be installed with the convex side facing upward during cutting attachment installation.
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