STIHL Trimmer Manual FS 55

The STIHL FS 55 is a lightweight, versatile gasoline-powered trimmer designed for residential and professional use. It features a 2-stroke engine with STIHL anti-vibration system, loop handle for comfortable operation, straight shaft, PolyCut head for easy line advancement, and a debris-deflecting clutch cover. This manual covers safety, features, assembly, operation, maintenance, and troubleshooting for the FS 55 trimmer.

Features at a Glance

Key components: 2-stroke engine, loop handle, straight drive shaft, PolyCut cutting head, debris-deflecting clutch cover, anti-vibration system.

Assembly & Preparation

Unpack and inspect all parts. Assemble on a clean, flat surface.

1. Attach the shaft: Connect the drive shaft to the powerhead, ensuring it clicks into place.
2. Install the handle: Slide the loop handle onto the shaft and tighten the clamping screws.
3. Attach the cutting head: Screw the PolyCut head onto the drive shaft end clockwise until secure.
4. Install the harness: Attach the shoulder harness according to the diagram for balanced operation.

WARNING! Always wear appropriate personal protective equipment (PPE) including eye protection, gloves, long pants, and sturdy boots during assembly and operation.

Fuel & Lubrication

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

1. Fuel mixture: Use STIHL MotoMix® pre-mixed fuel or mix STIHL 2-stroke engine oil at a 50:1 ratio (2.6 fl. oz. oil per 1 gallon gasoline).
2. Filling fuel: Clean area around cap. Fill fuel tank to about 80% capacity to allow for expansion.
3. Filling chain oil (if equipped with brushcutter attachment): Use STIHL HP Ultra chain oil or equivalent.
4. Check for leaks: Before starting, ensure all caps are tight and no fuel is leaking.

CAUTION! Fuel is highly flammable. Refuel outdoors, away from sparks or flames. Allow engine to cool before refueling.

Specifications

• Engine Type: STIHL 2-stroke, single-cylinder.
• Displacement: 27.2 cc.
• Power Output: 0.9 kW (1.2 bhp).
• Idle Speed: 2,800 rpm.
• Maximum Powerhead Speed: 11,500 rpm.
• Fuel/Oil Mix Ratio: 50:1.
• Sound Pressure Level: Approx. 96 dB(A).
• Vibration Level (left/right): Approx. 4.5/4.5 m/s².
• Warranty: Limited warranty for residential use.

Controls and Operation

Main controls: Throttle trigger, throttle trigger lockout, stop switch, choke lever, primer bulb.

Starting Procedure: 1. Move stop switch to "I" (Run) position. 2. Press and lock throttle trigger. Set choke lever to cold start position (if engine is cold). 3. Press primer bulb 5-10 times until fuel is visible. 4. Place trimmer on ground, hold securely. Pull starter rope briskly until engine fires. 5. Move choke lever to warm start position. Pull starter rope again to start. 6. Allow engine to warm up at idle for 30 seconds.

Operating: Hold with both hands. Use a sweeping motion from side to side, cutting with the tip of the line. Avoid hitting hard objects.

Cutting Attachments

Standard: STIHL PolyCut head with .095" (2.4mm) diameter trimmer line.

1. Advancing line: Tap head on ground while engine is at high idle (bump feed).
2. Replacing line: Remove spool, wind new line following directional arrows, feed ends through eyelets.
3. Optional attachments: STIHL circular grass blade or metal brush knife (require specific guard and kit).

Tip: Always stop the engine and disconnect the spark plug boot before changing or servicing the cutting attachment.

Maintenance Schedule

Supports long life with regular maintenance.

1. Daily: Clean air filter, check for loose fasteners, inspect cutting attachment.
2. Every 3 months: Clean spark arrestor screen (if equipped), check spark plug.
3. Every 6 months: Clean fuel filter, replace air filter if necessary.
4. Annually: Have unit serviced by an authorized STIHL dealer for carburetor adjustment and internal inspection.
5. General: Keep cooling fins clean, store properly.

WARNING! Use only STIHL approved replacement parts. Unauthorized parts may void warranty and cause unsafe operation.

Storage

For storage longer than 30 days, prepare the engine to prevent fuel system issues.

1. Add fuel stabilizer to fuel tank and run engine for 2 minutes to circulate.
2. Drain fuel tank and carburetor completely, or run engine until it stops from fuel starvation.
3. Remove spark plug, add a teaspoon of engine oil into cylinder, pull starter rope slowly to coat, reinstall plug.
4. Clean entire unit, store in a dry, secure place away from children.

CAUTION! Never store the trimmer with fuel in the tank indoors or in an enclosed space due to fire and fume hazards.

Safety Information

Read and understand the manual before use. Always wear PPE: safety glasses, hearing protection, gloves, long pants, sturdy boots. Keep bystanders and pets at least 50 feet away. Be aware of thrown object hazards. Never operate in wet conditions or near flammable materials.

Warranty & Support

STIHL Limited Warranty: Coverage varies by region and use (residential/commercial). Proof of purchase required. For support, contact an authorized STIHL servicing dealer or visit www.stihlusa.com. Keep this manual for future reference. Serial Number: Located on the engine housing.

Troubleshooting

Dealer Service: For repairs beyond basic maintenance, take the unit to an authorized STIHL dealer.

Support: www.stihlusa.com; Find a dealer locator on the website.