FS 80 Stihl Manual

The FS 80 is a professional-grade string trimmer/brushcutter from Stihl, featuring a powerful 2-stroke engine, lightweight design, and versatile cutting capabilities. This manual covers safety instructions, technical specifications, assembly, operation, maintenance, troubleshooting, and storage guidelines for optimal performance and user safety.

Safety Instructions

Read and understand all safety warnings before operation. Always wear appropriate PPE: safety glasses, hearing protection, gloves, long pants, and sturdy boots.

Hazard	Precaution
Kickback	Keep cutting attachment below waist level; maintain firm grip.
Flying Debris	Clear work area of bystanders; inspect area for hidden objects.
Fuel Handling	Refuel in well-ventilated area with engine off and cool.
Carbon Monoxide	Never operate in enclosed or poorly ventilated spaces.
Hot Surfaces	Avoid contact with muffler and cylinder during/after operation.

WARNING! Failure to follow safety instructions may result in serious injury or death.

Product Overview & Specifications

Key components: Engine, drive shaft, gearbox, cutting attachment, handlebar, harness.

• Engine Type: STIHL 2-stroke, single cylinder, 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.
• Sound Pressure Level: 96 dB(A).
• Vibration Level: 5.2 m/s².
• Recommended Fuel: STIHL MotoMix or 89+ octane gasoline with STIHL 2-stroke oil (50:1).

Assembly Instructions

Unpack all components and inspect for damage.

1. Attach handlebar: Align with mounting points and secure with provided bolts.
2. Install cutting attachment: Ensure gearbox is clean, attach trimmer head or blade, secure with retaining nut.
3. Adjust harness: Connect harness to unit, adjust for comfortable fit.
4. Fill fuel and oil: Use proper fuel mixture; fill chain oil if using brushcutter blade.

CAUTION! Ensure all fasteners are tightened to specified torque.

Fuel & Lubrication

Use only high-quality, unleaded gasoline (min. 89 octane) mixed with STIHL 2-stroke engine oil at 50:1 ratio.

1. Mix fuel in approved container: Add oil first, then gasoline. Shake thoroughly.
2. Fill fuel tank: Clean area around cap; use funnel to avoid spills.
3. Gearbox lubrication: Grease gearbox every 25 operating hours.
4. Drive shaft: Lubricate splines during assembly.

WARNING! Never use straight gasoline or automotive oil. Do not mix near open flame.

Starting & Stopping Procedure

Follow cold start procedure for initial use; warm start for hot engine.

Cold Start:

1. Set master control lever to START position.
2. Press primer bulb 5-10 times until fuel is visible.
3. Set choke lever to FULL CHOKE.
4. Pull starter rope sharply until engine fires.
5. Move choke lever to HALF CHOKE, pull again to start.
6. Allow to idle for 30 seconds before applying throttle.

Stopping: Release throttle, move master control lever to STOP.

Operating Instructions

Proper technique ensures efficiency and safety.

1. Harness adjustment: Adjust so unit hangs comfortably at hip level.
2. Cutting motion: Swing unit in smooth, sweeping arcs from right to left.
3. Cutting height: Keep cutting attachment parallel to ground; avoid digging into soil.
4. Trimming near obstacles: Use trimmer head guard; avoid contact with fences, trees.
5. Overhead clearance: Be aware of overhead power lines.

Tip: Work in sections, maintaining a steady pace to prevent overheating.

Cutting Attachment Guide

Select appropriate attachment for the task.

Attachment	Use Case	Precautions
STIHL PolyCut Head	General grass trimming, edging	Replace line when worn; avoid hard surfaces.
Circular Grass Blade	Tall grass, light weeds	Ensure blade is sharp; balance after sharpening.
Brush Knife	Heavy brush, saplings	Wear leg protection; use two-handed grip.
Metal Blade	Dense vegetation	Inspect for cracks; replace if damaged.

Maintenance Schedule

Regular maintenance ensures longevity and performance.

Interval	Task
Before each use	Inspect for loose fasteners, damage; check fuel level.
Every 25 hours	Clean air filter; check spark plug; grease gearbox.
Every 50 hours	Replace fuel filter; inspect drive shaft.
Every 100 hours	Clean cooling fins; check carburetor settings.
Annually	Full service by authorized STIHL dealer.

Storage Guidelines

Proper storage prevents fuel system issues and corrosion.

1. Short-term (under 30 days): Drain fuel tank and run engine until it stops.
2. Long-term: Drain fuel completely; remove spark plug; add teaspoon of oil to cylinder; pull starter slowly to distribute.
3. Clean unit thoroughly; store in dry, locked area away from children.
4. Remove cutting attachment; store separately.

CAUTION! Never store unit with fuel in tank for extended periods.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel, flooded, spark plug	Check fuel; dry spark plug; replace if fouled.
Engine runs poorly	Dirty air filter, fuel filter	Clean/replace air filter; replace fuel filter.
Excessive vibration	Unbalanced blade, loose parts	Balance blade; tighten all fasteners.
Cutting attachment stops	Drive shaft, gearbox	Inspect for damage; grease gearbox.
Overheating	Dirty cooling fins, lean mixture	Clean fins; adjust carburetor.

Warranty & Service

STIHL Limited Warranty: 1 year commercial use, 2 year residential use from date of purchase. Proof of purchase required.

For service: Contact authorized STIHL servicing dealer. Use only genuine STIHL replacement parts.

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