Stihl FS 80 Manual

The Stihl FS 80 is a professional-grade gasoline-powered brushcutter/string trimmer designed for demanding clearing and trimming tasks. It features a powerful 2-stroke engine with anti-vibration system, easy-start technology, a straight shaft with bicycle handles, a metal drive shaft, a PolyCut head for line trimming, 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, decompression valve for easy starting, straight shaft, bicycle handles, throttle trigger with lockout, stop switch, fuel tank, and attachment interface.

Feature	Description
Engine Type	Single cylinder, 2-stroke, air-cooled
Displacement	30.1 cm³ (1.84 cu. in.)
Power Output	Approx. 0.9 kW (1.2 hp)
Fuel System	Diaphragm carburetor
Starting System	Rewind starter with decompression valve
Drive Shaft	Solid metal, straight design
Anti-Vibration	Integrated dampers in handles and shaft
Cutting Attachment	Standard PolyCut head (line trimmer)
Handle System	Bicycle handles with adjustable harness
Weight (without cutting tool)	Approx. 5.9 kg (13.0 lbs)

Safety Instructions

Read and understand all instructions before use. Always wear appropriate PPE.

1. Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, sturdy gloves, long pants, and non-slip boots.
2. Work Area Safety: Clear area of bystanders, especially children and pets. Be aware of hidden obstacles like wires or stones.
3. Fuel Safety: Refuel outdoors only, with engine stopped and cool. Use approved fuel container. Wipe up spills immediately.
4. Operation: Hold unit firmly with both hands. Maintain secure footing. Do not operate above shoulder height.
5. Kickback Zone: Be aware of the danger zone to the right of the operator. Never use the machine with the cutting attachment near this zone.

WARNING! Failure to follow safety instructions can result in serious injury or death. The cutting tool continues to rotate after the throttle is released.

Assembly & Preparation

Unpack and inspect all parts. Assemble according to diagrams.

1. Handle Attachment: Slide handle onto shaft at desired position and tighten clamping screws securely.
2. Harness Attachment: Connect the harness rings to the hooks on the rear handle. Adjust straps for a snug, balanced fit.
3. Cutting Attachment: For PolyCut head: Ensure machine is off. Align head with drive shaft, push on, and turn clockwise until it clicks/locks. Pull to check it's secure.
4. Fuel Mix Preparation: Use STIHL 2-stroke engine oil mixed with unleaded gasoline (min. 89 octane) at a 50:1 ratio (2% oil). Shake container thoroughly.

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

Specifications

• Model: STIHL FS 80
• Engine Power: 0.9 kW (1.2 hp)
• Engine Displacement: 30.1 cm³
• Idle Speed: 2,800 rpm
• Max. Engine Speed: 12,500 rpm
• Fuel Tank Volume: 0.53 liters (18 fl. oz.)
• Oil Tank Volume (for gearbox): 0.1 liters (3.4 fl. oz.)
• Sound Pressure Level (LpA): 99 dB(A)
• Vibration Level (ah, handle): Left: 4.5 m/s², Right: 5.5 m/s²
• Warranty: Limited warranty for personal use. See manual for details.

Controls and Components

Main controls located on the handle unit.

Handle Unit: Throttle trigger, throttle trigger lockout (must be depressed to engage throttle), stop switch (I/O), choke lever (for starting), primer bulb.

Shaft & Engine: Decompression valve button (press before starting), fuel tank cap, oil tank cap (for gearbox lubrication), spark plug, air filter cover, muffler.

Harness: Adjustable shoulder straps and hip pad to distribute weight.

Fuel & Lubrication

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

1. Fueling: Place unit on stable ground. Clean area around cap. Open cap slowly. Use funnel. Fill to base of filler neck. Tighten cap securely.
2. Gearbox Lubrication: The gearbox at the end of the shaft must be filled with STIHL gear oil. Check level regularly and refill as needed.
3. Bar & Chain Oil (if using saw attachment): Use STIHL chain oil in the separate oil tank if a cut-off saw attachment is installed.

WARNING! Gasoline is extremely flammable. No smoking. Engine and exhaust are hot after use.

Starting & Operation

Follow cold or warm starting procedure.

1. Cold Start: Place unit on clear, flat ground. Press decompression valve. Set stop switch to "I". Set choke lever to closed position (✱). Press primer bulb 5-10 times. Pull starter rope sharply until engine 'fires'. Move choke lever to half-throttle position (⭘). Pull starter rope again to start. Allow to idle briefly before opening throttle.
2. Warm Start: Do not use choke. Set stop switch to "I". Pull starter rope.
3. Operation: Put on harness. Start unit on ground. Let engine warm up at idle for ~30 seconds. Use a smooth, sweeping motion from right to left (for right-handed operation), keeping cutting attachment parallel to ground. Do not force the tool.
4. Stopping: Release throttle and allow engine to idle. Press and hold stop switch ("O") until engine stops.

CAUTION! Never start the tool unless it is on the ground and you are in the operating position.

Cutting Attachments

Compatible with various STIHL attachments.

1. PolyCut Head (Standard): For trimming grass and weeds. Tap head on ground while at high idle to advance line ("Tap-n-Go").
2. Metal Blades: For clearing heavy brush, saplings, and thick weeds. Ensure correct blade (e.g., 4-tooth grass blade, circular saw blade) is installed and sharp. Always use blade guard and wear leg protection.
3. Cut-off Saw Attachment: For cutting stone, asphalt, or metal. Requires specific guard, blade, and use of both hand grips.
4. Changing Attachments: Stop engine. Wear gloves. Depress shaft lock button. Use appropriate wrench to loosen retaining nut (left-hand thread for some blades). Replace attachment and tighten nut securely.

WARNING! Use only attachments approved by STIHL for the FS 80. Ensure all guards are in place.

Maintenance & Storage

Regular maintenance ensures long life and safe operation.

1. Daily/After Use: Clean exterior, check for loose fasteners, check cutting attachment for damage/wear.
2. Air Filter: Clean regularly (tap out dirt) or replace if clogged. Do not run engine without filter.
3. Spark Plug: Check and clean electrode gap (0.5 mm / 0.020 in) periodically. Replace if worn.
4. Fuel Filter: Replace annually or if clogged.
5. Storage (>30 days): Drain fuel tank and run carburetor dry. Remove spark plug, add a few drops of oil into cylinder, pull starter slowly 2-3 times, reinstall plug. Clean entire unit. Store in dry, secure place.

CAUTION! Perform maintenance only when engine is cool and spark plug wire is disconnected.

Warranty Information

STIHL Limited Warranty: The STIHL FS 80 is backed by a limited warranty for personal use. The warranty period and terms vary by region. Proof of purchase from an authorized STIHL dealer is required. Warranty does not cover damage from misuse, neglect, improper fuel, or unauthorized repairs. For full warranty details, contact your local authorized STIHL dealer or visit www.stihlusa.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, spark plug faulty, switch off, choke incorrect	Check fuel, dry spark plug, ensure switch is on, use correct choke setting.
Engine starts but dies	Clogged fuel filter, dirty air filter, carburetor adjustment	Replace fuel filter, clean air filter, have dealer adjust carburetor.
Loss of power	Dirty air filter, clogged muffler screen, old fuel	Clean air filter, clean spark arrestor screen, use fresh fuel mix.
Excessive vibration	Loose fasteners, bent shaft, unbalanced/damaged blade	Tighten all screws/nuts, inspect shaft and cutting attachment for damage.
Line does not advance	Empty spool, line tangled, worn bump head	Refill spool with correct line, untangle, replace head if worn.
Cutting attachment spins at idle	Idle speed too high	Have authorized dealer adjust idle speed (carburetor adjustment).

Service: For repairs beyond basic maintenance, contact an authorized STIHL servicing dealer. Use only genuine STIHL parts.

Support: www.stihlusa.com or contact your local authorized STIHL dealer.