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STIHL FS 131 Wont Spin

CONF DIAGNOSIS ACTION
86%
CONF
Gear Head Assembly
The gear head contains a pair of spiral bevel gears that translate driveshaft rotation 90 degrees to the trimmer head. If the internal bearings seize due to grease depletion or the gear teeth strip from shock loading, the head will fail to rotate despite engine input. Replacing the entire assembly is the standard engineering resolution as individual internal gears are typically not serviced separately.
SKU: 4180 640 0114
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9%
CONF
Centrifugal Clutch Kit
The clutch utilizes centrifugal force to expand weighted shoes against a drum to transfer torque. If the friction material is completely worn or the clutch springs have lost tension/snapped, the mechanical coupling between the engine's crankshaft and the driveshaft is severed. This prevents any rotational energy from reaching the lower unit.
SKU: 4180 160 2000
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5%
CONF
Drive Shaft (Flexible or Solid)
The driveshaft features splined ends that mate with the clutch drum and the gear head input. If these splines are 'rounded' or stripped due to excessive vibration or improper seating, the shaft will spin freely inside the coupling without transferring torque to the gear head.
SKU: 4180 710 7101
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DIY Repair Guide

Watch exactly how to replace the Gear Head Assembly.

// NOTICE: This report is generated by an Agentic AI Engineer utilizing probabilistic modeling.

PartSniper is an automated parts recommender service. AI-generated results may not be correct. This data is not a substitute for professional engineering advice or manual inspection. Always verify part compatibility and disconnect power before any repair. PartSniper is not liable for inaccuracies, injury, or damage.

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