FS 85 STIHL Manual

The FS 85 is a professional-grade gasoline-powered string trimmer/brushcutter from STIHL, designed for demanding clearing and trimming tasks. It features a lightweight yet powerful 2-stroke engine, anti-vibration system, ergonomic handles, adjustable harness, and compatibility with various cutting attachments. Below are key sections for safety, features, operation, maintenance, troubleshooting, and specifications.

Features at a Glance

Key components: 2-stroke engine, anti-vibration system, ErgoStart™, adjustable harness, loop handle, straight shaft, and quick-release cutting head.

Feature	Description
Engine Type	STIHL 2-MIX™ 2-stroke, air-cooled
Displacement	27.2 cc
Power Output	0.9 kW (1.2 hp)
Fuel Tank Capacity	0.53 liters
Weight (without cutting attachment)	5.2 kg
Shaft Type	Straight, solid drive shaft
Anti-Vibration System	Integrated dampers in handle and shaft
Starting System	ErgoStart™ for easy pull
Cutting Attachment	Quick-release for easy change
Harness	Adjustable comfort harness included

Safety Instructions

Read all instructions before operation. Wear proper PPE.

1. Personal Protective Equipment: Always wear safety glasses, hearing protection, gloves, long pants, and sturdy boots.
2. Clear Work Area: Remove stones, nails, wire, and other debris before starting.
3. Fuel Safety: Refuel outdoors only, with engine stopped and cool. Use STIHL MotoMix or proper fuel/oil mix.
4. Operation Zone: Keep bystanders and pets at least 15 meters away.
5. Hot Surfaces: Avoid contact with muffler and cylinder during/after operation.

WARNING! Risk of serious injury or death. Never operate without proper training and PPE. Do not modify the unit.

Assembly & Preparation

Unpack and inspect contents. Assemble according to instructions.

1. Attach handle: Secure loop handle to shaft at comfortable position.
2. Install harness: Connect harness D-rings to unit attachment points.
3. Mount cutting attachment: Align quick-release head and lock securely.
4. Fuel mix: Use STIHL 2-stroke engine oil at 50:1 ratio (or MotoMix pre-mix).
5. Check controls: Ensure throttle trigger, stop switch, and throttle lockout function properly.

CAUTION! Ensure all fasteners are tight before operation. Use only STIHL-approved attachments.

Technical Specifications

• Engine: STIHL 2-MIX™, 27.2 cc, single cylinder.
• Powerhead Weight: 5.2 kg (without cutting attachment).
• Fuel/Oil Ratio: 50:1 (STIHL 2-stroke oil) or use STIHL MotoMix.
• Sound Pressure Level: 96 dB(A) typical.
• Vibration Levels: Left handle: 4.2 m/s²; Right handle: 5.8 m/s².
• Recommended Cutting Attachments: STIHL PolyCut head, metal blade, brush knife.
• Warranty: Limited commercial warranty (see manual).
• Emissions Compliance: Meets EPA Phase II and EU Stage II standards.

Controls and Components

Main controls located on handle and engine housing.

Handle Area: Throttle trigger, throttle lockout, stop switch, harness attachment points.

Engine Housing: Starter grip, choke lever, fuel tank cap, air filter cover, spark plug.

Shaft: Drive shaft inside tubular housing, anti-vibration mounts.

Cutting Head: Quick-release mechanism, line feed button (if equipped), guard.

Adjustments: Handle angle, harness length, guard position.

Starting & Stopping Procedure

Follow proper sequence to avoid damage and ensure safety.

1. Pre-start check: Ensure area clear, harness adjusted, attachment secure.
2. Fuel: Check level. Prime if equipped (press bulb 5-10 times).
3. Choke: Move lever to cold start position (full choke).
4. Ignition: Set stop switch to "I" (run) position.
5. Starting: Place unit on ground, hold securely. Pull starter rope slowly until resistance, then briskly. After engine fires, move choke to half or run.
6. Warm-up: Allow 30-60 seconds at idle before operation.
7. Stopping: Release throttle, allow idle, move stop switch to "0" (stop).

Tip: Do not pull starter rope to full extension; do not let starter snap back.

Operating Instructions

Use proper technique for efficiency and safety.

1. Harness: Adjust so unit hangs comfortably; use hips to swing, not arms.
2. Swing arc: Use a smooth, controlled side-to-side motion, keeping cutting head parallel to ground.
3. Cutting height: Trim grass just above ground; for weeds, use tip of line/blade.
4. Feed line: Tap head on ground at full throttle to advance trimmer line (if equipped).
5. Avoid kickback: Do not use metal blade near fences, trees, or hard objects.
6. Slopes: Work across slopes, not up and down. Maintain secure footing.
7. Fatigue: Take breaks every 30-45 minutes.

WARNING! Never operate above shoulder height. Be aware of thrown debris.

Maintenance Schedule

Regular maintenance ensures long life and safe operation.

Interval	Task
Daily/Before Use	Check for loose fasteners, leaks, damage. Clean air filter if dirty.
Every 25 hours	Clean spark arrestor screen (if equipped). Check fuel filter.
Every 50 hours	Replace spark plug. Clean cooling fins. Check anti-vibration elements.
Every 100 hours	Replace fuel filter. Clean carburetor (or as needed). Inspect drive shaft.
As needed	Sharpen/replace blade. Replace trimmer line. Grease gearhead (if equipped).

CAUTION! Disconnect spark plug wire before performing maintenance.

Storage Guidelines

Prepare unit for storage to prevent fuel system issues.

1. Short-term (under 30 days): Run carburetor dry or add fuel stabilizer.
2. Long-term: Drain fuel tank completely. Run engine until it stops to dry carburetor.
3. Clean: Remove debris from cooling fins, air filter, and exterior.
4. Store: In dry, locked area, out of reach of children. Cover to prevent dust.
5. Battery (if electric start): Remove and charge periodically.

CAUTION! Store fuel in approved container, away from heat and sparks.

Warranty Information

STIHL Limited Warranty: 1-year commercial warranty from date of purchase. Proof of purchase required. Warranty covers defects in materials and workmanship. Not covered: normal wear, misuse, improper maintenance, non-STIHL parts. For warranty service, contact an authorized STIHL servicing dealer. For support, visit www.stihlusa.com or call 1-800-467-8445.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel, flooded, spark plug	Check fuel; wait if flooded; clean/replace spark plug.
Engine runs poorly/dies	Dirty air filter, old fuel	Clean air filter; drain and replace with fresh fuel mix.
Excessive vibration	Loose parts, bent shaft, unbalanced blade	Tighten fasteners; inspect shaft; balance/replace blade.
Line not feeding	Empty spool, tangled line	Reload with correct line size; untangle or replace spool.
Loss of power	Clogged fuel filter, exhaust screen	Replace fuel filter; clean spark arrestor screen.

Dealer Service: For complex repairs, contact authorized STIHL dealer.

Support: 1-800-467-8445; www.stihlusa.com