FS 86 STIHL Manual

The FS 86 is a professional-grade gasoline-powered string trimmer/brushcutter from STIHL, designed for demanding vegetation control applications. It features a powerful 2-stroke engine with STIHL anti-vibration system, ErgoStart™ for easy starting, a translucent fuel tank, adjustable loop handle, and compatibility with various cutting attachments. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 2-stroke engine with ErgoStart™, anti-vibration system, translucent fuel tank, adjustable loop handle, throttle trigger lockout, and quick-release shaft coupling.

Feature	Description
Engine Type	STIHL 2-stroke, single cylinder, air-cooled
Displacement	27.2 cc (1.66 cu. in.)
Power Output	0.9 kW (1.2 bhp)
Fuel Tank Capacity	0.53 liters (18 fl. oz.)
Weight (without cutting attachment)	5.4 kg (11.9 lbs)
Anti-Vibration System	STIHL standard dampening elements
Starting System	STIHL ErgoStart™
Drive Shaft	Solid, with quick-release coupling
Handle System	Adjustable loop handle
Throttle Control	Trigger with lockout for safety

Safety Information

Read and understand all instructions before operation. Wear proper PPE.

1. Personal Protective Equipment: Always wear safety glasses, hearing protection, sturdy gloves, long pants, and boots.
2. Clear Work Area: Remove stones, nails, wire, and other debris that could be thrown.
3. Fuel Safety: Refuel outdoors only, with engine stopped and cool. Use STIHL MotoMix® or proper fuel/oil mix.
4. Operation: Keep bystanders and pets at least 15 meters away. Hold unit firmly with both hands.

WARNING! Risk of severe injury or death from rotating cutting attachment. Never operate without proper guard installed.

Assembly & Preparation

Unpack and inspect contents. Assemble according to instructions.

1. Attach Shaft: Connect drive shaft sections, ensuring quick-release coupling clicks securely.
2. Install Handle: Slide loop handle onto shaft and tighten clamping screws.
3. Install Cutting Attachment: Attach trimmer head or blade, ensuring it is secured with proper nut and guard.
4. Fuel Mix: Use STIHL MotoMix® (50:1) or mix high-quality 2-stroke oil with unleaded gasoline (min. 89 octane) at 50:1 ratio.

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

Specifications

• Engine: STIHL 2-stroke, 27.2 cc.
• Fuel/Oil Ratio: 50:1 (STIHL MotoMix® recommended).
• Sound Power Level: 107 dB(A).
• Vibration Levels: Left handle: 4.5 m/s², Right handle: 5.5 m/s².
• Cutting Width (with standard trimmer head): Approx. 430 mm (17 in).
• Recommended Attachments: STIHL PolyCut head, circular grass blades, brush knife.
• Warranty: Limited warranty, see STIHL dealer for details.
• Compliance: Meets ANSI B175.3 and EPA Phase II emissions standards.

Controls and Components

Main components: Throttle trigger with lockout, STOP switch, choke lever, primer bulb, fuel tank cap, spark plug boot.

Handle Area: Throttle trigger lockout must be depressed before throttle can be engaged. STOP switch stops engine.

Starting Procedure: Move master control lever to choke position (cold start). Press primer bulb 5-10 times. Pull starter handle sharply. Adjust choke as engine fires.

Fuel & Lubrication

Use fresh, unleaded gasoline with minimum 89 octane. Mix with STIHL 2-stroke engine oil at 50:1 ratio.

1. Fueling: Clean area around cap. Use funnel. Fill to level indicated on translucent tank.
2. Gearbox Lubrication: Lubricate gearbox with STIHL gear grease after every 25 hours of operation.
3. Air Filter: Check before each use; clean with compressed air or replace if dirty.

Tip: For best performance and engine life, use STIHL MotoMix® pre-mixed fuel.

Starting & Operation

Starting (Cold Engine):

1. Place unit on clear, flat ground.
2. Press fuel primer bulb until fuel is visible.
3. Set master control lever to choke position.
4. Depress throttle trigger lockout and pull throttle trigger. Hold trigger open while setting master control to half-throttle position.
5. Hold unit securely with one hand on handle, foot in rear handle. Pull starter cord briskly until engine fires.
6. Move master control to run position. Allow engine to warm up at idle.

Operation: Swing trimmer in arc from right to left, keeping cutting head parallel to ground. Do not force tool; let tip speed do the work.

Cutting Attachments

STIHL PolyCut Head: For trimming grass and light weeds. Tap head on ground to advance line.

Circular Grass Blades: For heavy grass and weeds. Ensure proper guard is installed.

Brush Knife: For clearing saplings and heavy brush.

WARNING! Always stop engine and ensure cutting attachment has stopped before changing attachments or clearing debris.

Maintenance & Storage

Daily: Clean exterior, check for loose fasteners, inspect cutting attachment and guard.

Weekly: Check air filter, clean spark arrestor screen (if equipped).

Storage: For long-term storage, run engine dry of fuel or add fuel stabilizer. Store in dry, secure location.

CAUTION! Disconnect spark plug boot before performing any maintenance.

Regulatory Information

This STIHL power tool meets applicable ANSI/OPEI safety standards and EPA emissions regulations. The engine exhaust from this product contains chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm. For warranty service, contact an authorized STIHL servicing dealer. © STIHL Incorporated. STIHL is a registered trademark.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, spark plug	Check fuel level; set choke to run and pull starter repeatedly; check/clean spark plug.
Engine runs poorly, lacks power	Dirty air filter, clogged fuel filter, old fuel	Clean/replace air filter; replace fuel filter; use fresh fuel mix.
Excessive vibration	Damaged cutting attachment, loose parts	Inspect blade/head for damage; tighten all fasteners.
Line not advancing	Worn head, tangled line	Replace trimmer head; remove spool and untangle line.
Engine overheats	Dirty cooling fins, lean fuel mix	Clean cylinder fins; ensure proper fuel/oil mix.

Service: For repairs, contact an authorized STIHL dealer. Use only STIHL replacement parts.

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