STIHL FS55R Owner's Manual

The STIHL FS55R is a lightweight, professional-grade straight-shaft grass trimmer/brushcutter designed for demanding clearing and trimming tasks. It features a powerful 2-stroke engine with STIHL anti-vibration system, ErgoStart™ for easy starting, a loop handle for comfortable operation, a straight shaft for extended reach, and a Tap-n-Go™ semi-automatic cutting head line advance system. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: STIHL 2-stroke engine, ErgoStart™ system, anti-vibration handles, straight drive shaft, Tap-n-Go™ cutting head, loop handle, and throttle trigger lockout.

Feature	Description
Engine	STIHL 2-stroke, single-cylinder, air-cooled
Starting System	ErgoStart™ for reduced pulling force
Anti-Vibration	STIHL anti-vibration system in handles and shaft
Drive Shaft	Straight solid shaft for durability and reach
Cutting Head	Tap-n-Go™ semi-automatic line advance
Handle	Loop handle with throttle trigger and lockout
Fuel System	Diaphragm carburetor with purge bulb
Spark Arrestor	Muffler with USDA approved spark arrestor screen
Decompression Valve	Eases starting by reducing cylinder pressure
Warranty	STIHL limited warranty (see manual for details)

Safety Information

Read and understand all instructions before operation. Always wear appropriate Personal Protective Equipment (PPE).

1. PPE Required: Safety glasses, hearing protection, heavy-duty gloves, long pants, sturdy boots.
2. Clear Work Area: Remove stones, nails, wire, and other debris that could be thrown.
3. Fuel Safety: Refuel outdoors, away from sparks/flames. Engine must be cool. Use STIHL MotoMix® or 50:1 mix with high-quality 2-stroke oil.
4. Operation: Keep bystanders and pets at least 50 feet away. Hold unit firmly with both hands.
5. Kickback Zone: Be aware of the dangerous zone (approx. 2 o'clock to 12 o'clock position of cutting head).

WARNING! Improper use can cause serious or fatal injury. This is a high-speed cutting tool. Never operate without proper guards and equipment.

Assembly & First Use

Unpack all parts. Assembly requires attaching the handle, cutting attachment, and shoulder strap.

1. Handle Attachment: Position loop handle on shaft, align, and tighten clamping screws securely.
2. Cutting Attachment: Install cutting head or blade per instructions, ensuring deflector/shield is correctly mounted and secure.
3. Shoulder Strap: Attach STIHL harness or shoulder strap for balanced operation and reduced fatigue.
4. Fuel Mix: Fill fuel tank with STIHL MotoMix® (pre-mixed) or a 50:1 gasoline to 2-stroke oil mixture.
5. Initial Start: Follow starting procedure. Allow engine to warm up at idle for 30 seconds.

CAUTION! Ensure all fasteners are tight before starting. Do not operate with loose components.

Specifications

• Engine Displacement: 27.2 cc (1.7 cu. in.)
• Power Output: 0.9 kW (1.2 bhp)
• Fuel Tank Capacity: 0.53 L (18 fl. oz.)
• Weight (without cutting attachment): 5.4 kg (11.9 lbs)
• Shaft Type: Straight solid shaft
• Recommended Cutting Attachments: STIHL PolyCut™ head, circular grass blades, brush knives
• Sound Power Level (LWA): 112 dB(A)
• Vibration Levels (ah, ah): Left handle: 4.5 m/s², Right handle: 6.5 m/s²
• Warranty: STIHL Limited Warranty for private users

Controls and Components

Main controls located on the loop handle and engine housing.

Handle Area: Throttle trigger, throttle trigger lockout (must be depressed to engage throttle), stop switch (I/O).

Engine Housing: ErgoStart™ starter grip, choke lever (⏚ / ●), decompression valve button, purge bulb (primer), fuel tank cap, ON/OFF switch.

Shaft/Cutting End: Gearhead housing, deflector, cutting attachment (head or blade), shaft coupling.

Fuel & Lubrication

Use only high-quality, unleaded gasoline with a minimum octane rating of 89 (RON).

1. Fuel Mix Ratio: 50:1 (2% oil). Use STIHL 2-Stroke Engine Oil or an ISO-L-EGD and JASO FD certified oil.
2. Pre-Mixed Option: STIHL MotoMix® is recommended to ensure correct mix and fuel freshness.
3. Mixing: Add oil to an approved fuel can, then add gasoline. Shake well before filling unit.
4. Gearhead Grease: Lubricate gearhead with STIHL grease cartridge after every 25 hours of operation.

Tip: Never use fuel older than 60 days. Ethanol-blended fuels can cause damage; use fuel stabilizer if required.

Starting & Stopping the Engine

Cold Start Procedure:

1. Press fuel tank purge bulb 5-10 times until fuel is visible.
2. Set stop switch to "I" (ON).
3. Push in decompression valve (if equipped).
4. Set choke lever to ⏚ (cold start/choke position).
5. Place unit on firm ground. Hold handle firmly with left hand, place right foot in rear handle.
6. Pull starter rope briskly until engine fires (usually 1-3 pulls).
7. Move choke lever to ● (run/half-throttle) position immediately.
8. Pull starter rope again to start engine. Allow to warm up at idle.

Warm Start: Omit steps 4 and 7. Start with choke in ● position.

Stopping: Release throttle, allow engine to idle briefly, then move stop switch to "O" (OFF).

Operating Instructions

Always maintain secure footing and balance. Use a swinging, scything motion from right to left.

1. Trimming Technique: Hold cutter head parallel to ground. Cut from right to left for best debris discharge.
2. Line Advance (Tap-n-Go™): Gently tap cutting head on ground at operating RPM to advance fresh line.
3. Tall Grass/Brush: Use a slower, overlapping sweeping motion. For heavy brush, use appropriate metal blade.
4. Avoiding Kickback: Never swing unit so the cutting attachment contacts an object in the 12 to 2 o'clock position.
5. Fatigue Reduction: Use shoulder strap, take frequent breaks, and switch sides periodically.

WARNING! Do not operate the unit with one hand. Always be aware of your surroundings and the location of the cutting head.

Maintenance Schedule

Interval	Task
Before each use	Inspect for loose fasteners, damage. Check cutting attachment security.
Daily	Clean air filter (more often in dusty conditions). Check fuel lines.
Every 25 hours	Lubricate gearhead with STIHL grease. Clean spark arrestor screen.
Every 50 hours	Replace spark plug. Check fuel filter.
Every 100 hours	Clean combustion chamber. Have unit inspected by STIHL dealer.
As needed	Replace cutting line. Sharpen or replace metal blades.

CAUTION! Disconnect spark plug boot before performing any maintenance.

Storage

For storage longer than 30 days, prepare the unit to prevent fuel system damage.

1. Drain fuel tank completely and run engine until it stops to empty carburetor.
2. Remove spark plug, add a teaspoon of 2-stroke oil into cylinder, pull starter rope slowly 2-3 times, reinstall plug.
3. Clean entire unit thoroughly, especially cooling fins and air intake.
4. Store in a dry, secure place, out of reach of children.

Tip: Using STIHL MotoMix® can reduce storage preparation needs due to its extended shelf life.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, spark plug faulty, switch OFF	Check fuel, dry plug, check spark, ensure switch is ON.
Engine starts then dies	Clogged fuel filter, dirty air filter, vent blocked	Replace fuel filter, clean air filter, check tank vent.
Loss of power	Clogged air filter, dirty spark arrestor, old fuel	Clean/replace air filter, clean spark arrestor screen, use fresh fuel.
Excessive vibration	Loose cutting attachment, bent shaft, damaged blade	Tighten attachment, inspect shaft and blade for damage.
Line does not advance	Empty spool, tangled line, worn bump knob	Reload spool with correct line, untangle, replace knob if worn.

Service: For repairs beyond basic maintenance, contact an authorized STIHL servicing dealer.

Support: Visit www.stihlusa.com or call 1-800-467-8445 for dealer locations and support.