Stihl FS50 Trimmer Manual

The Stihl FS50 is a lightweight, straight-shaft grass trimmer designed for residential use. It features a reliable 2-stroke engine, a loop handle for comfortable operation, a Tap 'n Go™ semi-automatic line advance system, and a PolyCut™ head for easy line replacement. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 2-stroke engine, straight shaft, loop handle, Tap 'n Go™ cutting head, PolyCut™ head, throttle trigger lockout, and fuel tank.

Safety Information

Read all instructions before operation. Wear appropriate PPE.

1. Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, long pants, sturdy boots, and gloves.
2. Clear Work Area: Remove stones, sticks, wire, and other debris before trimming.
3. Fuel Safety: Refuel in a well-ventilated area with engine off and cool. Use only STIHL MotoMix® or a 50:1 gasoline/oil mixture.
4. Operation: Keep bystanders and pets at least 50 feet away. Do not operate in wet conditions.
5. Hot Surfaces: Avoid contact with muffler and cylinder during and after operation.

WARNING! Risk of serious injury or death from rotating cutting line. Keep hands and feet away from cutting head at all times.

Assembly & First Use

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

1. Handle Attachment: Slide handle onto shaft at desired position. Tighten clamping screws securely.
2. Cutting Head Installation: Remove protective cap from shaft end. Thread PolyCut™ head onto shaft clockwise until hand-tight.
3. Shoulder Strap: Attach hook to ring on rear of machine. Adjust strap for comfortable, balanced operation.
4. Fuel Mix: Fill tank with STIHL MotoMix® (pre-mixed) or a 50:1 mix of unleaded gasoline (min. 89 octane) and STIHL 2-stroke oil.
5. Starting: Place unit on clear, flat ground. Set stop switch to "I". Press primer bulb 5 times. Pull starter cord smoothly until engine starts.

CAUTION! Ensure all fasteners are tight before operation. Do not force parts during assembly.

Specifications

• Engine Displacement: 27.2 cc
• Engine Power: 0.9 kW (1.2 bhp)
• Fuel/Oil Ratio: 50:1 (using STIHL 2-stroke oil)
• Fuel Tank Capacity: 0.42 US pt (0.2 liter)
• Sound Pressure Level: 94 dB(A) (measured per EN ISO 22868)
• Vibration Level: Left/Right Handle: 4.5/6.5 m/s² (measured per EN ISO 22867)
• Cutting Swath: Approx. 16 inches (40 cm) with monofilament line
• Drive System: Solid steel shaft with gearhead
• Warranty: Limited warranty for residential use (see manual for details)

Controls and Components

Familiarize yourself with all controls before starting.

Main Controls:

• Throttle Trigger: Controls engine speed. Release to idle.
• Throttle Trigger Lockout: Must be depressed before throttle can be engaged.
• Stop Switch: Move to "0" or "STOP" to stop engine.
• Choke Lever: Used for cold starting (position ●).
• Primer Bulb: Press to draw fuel into carburetor for easier starting.
• Tap 'n Go™ Button: Tap head on ground while engine is running to advance cutting line.

CAUTION! Never attempt to adjust the carburetor. All adjustments must be performed by an authorized STIHL servicing dealer.

Operation

Operate the trimmer using a smooth, sweeping motion.

1. Starting (Cold Engine): Set stop switch to "I". Move choke lever to ●. Press primer bulb 5 times. Pull starter cord briskly until engine fires. Move choke lever to ø. Pull starter cord again to start. Allow 30-second warm-up.
2. Starting (Warm Engine): Follow steps above but leave choke at ø.
3. Line Advance: While engine is running at high speed, tap cutting head firmly on bare ground. Do not "bounce".
4. Cutting Technique: Hold trimmer so line is parallel to ground. Use a right-to-left sweeping motion, cutting with the tip of the line. Avoid pushing head into dense growth.
5. Stopping: Release throttle trigger. Allow engine to idle for 10 seconds. Move stop switch to "0".

Tip: For best cutting performance and line life, advance line before it becomes excessively worn.

Maintenance & Cleaning

Regular maintenance ensures long life and safe operation. Always disconnect spark plug boot before performing maintenance.

1. After Each Use: Wipe down exterior with a clean, dry cloth. Inspect for loose fasteners or damage.
2. Air Filter: Clean weekly under normal conditions, more often in dusty environments. Remove filter, tap clean, or wash in soapy water. Allow to dry completely before reinstalling.
3. Spark Plug: Check and clean electrode every 50 hours. Replace if electrode is worn or damaged. Gap: 0.020" (0.5 mm).
4. Cutting Head: Replace PolyCut™ spool when line is depleted. Use only STIHL genuine .095" diameter monofilament line.
5. Gearhead Grease: Lubricate gearhead every 25 hours of operation using STIHL special gear grease.

CAUTION! Never use water or pressurized air to clean the engine or air filter. Always use genuine STIHL parts.

Storage

Prepare unit for storage if it will not be used for more than 30 days.

1. Drain fuel tank completely and run engine until it stops to empty carburetor.
2. Clean entire unit thoroughly.
3. Remove spark plug and pour one teaspoon of engine oil into cylinder. Pull starter cord slowly to distribute oil, then reinstall plug.
4. Store in a cool, dry place, out of reach of children, and away from ignition sources.

WARNING! Storing fuel in the unit for long periods can cause gum deposits in the carburetor and fuel system.

Troubleshooting

Note: For repairs not listed, contact an authorized STIHL servicing dealer.

Warranty & Support

The STIHL FS50 is covered by a limited warranty for residential use. Proof of purchase from an authorized STIHL dealer is required.

For Service: Repairs should be performed only by an authorized STIHL servicing dealer using genuine STIHL parts.

For Support: Contact STIHL Incorporated at 1-800-467-8445 or visit www.stihlusa.com for dealer locations, manuals, and safety information.

Safety & Instructional Videos: Available on the official STIHL YouTube channel.