Stihl FS 38 Owner's Manual

The Stihl FS 38 is a lightweight, easy-to-handle gasoline-powered string trimmer designed for residential use. It features a reliable 2-stroke engine, a straight shaft, a loop handle with integrated controls, a Tap Advance™ cutting head for easy line feed, and a debris shield. This manual covers safety instructions, assembly, operation, maintenance, troubleshooting, and specifications to ensure safe and efficient use.

1. Safety Instructions 2. Assembly & Preparation 3. Controls & Features 4. Operation 5. Maintenance & Cleaning 6. Storage 7. Troubleshooting 8. Specifications

Safety Instructions

Read and understand all instructions before use. Failure to follow warnings can result in serious injury or death.

Hazard	Precaution
Kickback & Thrown Objects	Always wear eye and hearing protection, long pants, and sturdy boots. Keep bystanders at least 50 feet away.
Fire & Explosion	Fuel only in well-ventilated area, away from sparks or flames. Use approved fuel container. Do not smoke.
Carbon Monoxide	Operate only in well-ventilated outdoor areas. Never use indoors.
Vibration	Take regular breaks to reduce risk of hand-arm vibration syndrome.
Hot Surfaces	Allow engine and muffler to cool before touching or performing maintenance.

WARNING! This tool produces intense, rapid vibrations. Operators with circulation problems or who take certain medications should consult a physician before use.

Assembly & Preparation

Unpack all parts and inspect for damage. Assembly requires attaching the handle, installing the debris shield, and filling with fuel/oil mixture.

Handle Attachment: Align handle on shaft at comfortable operating height. Secure with provided bolts and wrench.
Debris Shield: Slide shield onto shaft and secure according to diagram in manual.
Cutting Head: Pre-wound spool is installed. For replacement, follow instructions in maintenance section.
Fuel Mix: Use only 50:1 mixture of unleaded gasoline (min. 89 octane) and STIHL 2-stroke engine oil. Do not use automotive oil or old fuel.

CAUTION! Ensure all fasteners are tight before starting. Loose parts can become dangerous projectiles.

Controls & Features

Familiarize yourself with all controls before starting the engine.

Control/Feature	Description
Throttle Trigger	Located on the handle. Squeeze to increase engine speed.
Throttle Trigger Lockout	Must be depressed before throttle trigger can be engaged. Safety feature to prevent accidental acceleration.
Stop Switch	Moves to "I" (On) or "O" (Off) position.
Choke Lever	Used for cold starting. Move to full choke position.
Purge Bulb (Primer)	Press several times before cold start to fill carburetor with fuel.
Tap Advance™ Cutting Head	Bump head on ground while engine is running to advance cutting line.
Loop Handle	Provides comfortable two-handed control and vibration damping.

Operation

Follow these steps for safe and effective trimming and brush cutting.

Starting:
- Place unit on clear, flat ground.
- Set stop switch to "I". Move choke lever to full choke (cold engine).
- Press purge bulb 5-6 times until fuel is visible.
- Hold unit securely. Pull starter rope briskly until engine fires.
- Move choke lever to half-choke and pull again to start. Warm engine: Start with choke off.
Trimming Technique:
- Hold trimmer with right hand on throttle handle, left hand on auxiliary handle.
- Use a smooth, sweeping motion from side to side, keeping cutting head parallel to ground.
- Allow tip of line to do the cutting. Do not force tool.
- To advance line, tap cutting head firmly on ground at operating speed.
Stopping: Release throttle trigger. Move stop switch to "O".

WARNING! Never operate the tool with a damaged shield or without the shield in place. Always shut off engine before setting tool down.

Maintenance & Cleaning

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

Air Filter: Clean weekly under normal conditions, more often in dusty environments. Remove, tap clean, or wash in soapy water. Dry completely before reinstalling.
Spark Plug: Check and clean electrode gap (0.020 in / 0.5 mm) every 50 operating hours. Replace if worn or fouled.
Fuel Filter: Replace annually or if fuel flow is restricted.
Cutting Head: Replace line spool when line is worn short. Ensure all pieces of old line are removed. Follow winding diagram inside spool cover.
Exterior: Keep unit clean. Wipe with a dry cloth. Remove debris from cooling fins, air intake, and shield.
Shaft & Gear Housing: Lubricate drive shaft and gear housing with STIHL grease every 50 hours or seasonally.

Storage

Proper storage prevents fuel system problems and corrosion.

Short Term (under 30 days): Store unit in a dry, secure place out of reach of children.
Long Term (Seasonal):
- Drain fuel tank completely and run engine until it stops to clear carburetor.
- Remove spark plug, add a teaspoon of engine oil into cylinder, pull starter rope slowly 2-3 times, reinstall plug.
- Clean entire unit thoroughly.
- Store in a dry, covered location.

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

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	1. Stop switch off. 2. No fuel. 3. Flooded engine. 4. Dirty air filter. 5. Faulty spark plug.	1. Set switch to "I". 2. Fill with fresh fuel mix. 3. Move choke to off, hold throttle open, pull starter repeatedly. 4. Clean or replace filter. 5. Clean, gap, or replace plug.
Engine runs poorly or stalls	1. Dirty fuel filter. 2. Clogged fuel tank vent. 3. Carburetor adjustment needed.	1. Replace fuel filter. 2. Clean tank cap vent. 3. Have serviced by authorized STIHL dealer.
Line does not advance	1. Line worn too short. 2. Spool jammed or empty. 3. Incorrect bump technique.	1. Tap head to advance. If no line, replace spool. 2. Clean head and reload spool. 3. Bump firmly on flat ground at high speed.
Excessive vibration	1. Loose fasteners or parts. 2. Bent drive shaft. 3. Damaged cutting head.	1. Tighten all bolts and nuts. 2. Inspect shaft. Replace if bent. 3. Replace cutting head assembly.

Specifications

Model: STIHL FS 38
Engine Type: Air-cooled, 2-stroke, single cylinder
Displacement: 27.2 cc (1.7 cu. in.)
Powerhead Weight: 4.9 kg (10.8 lbs)
Shaft Type: Straight, solid drive shaft
Cutting Swath: Approx. 16 in. (40 cm) with monofilament line
Fuel/Oil Ratio: 50:1 (STIHL 2-Stroke Oil)
Fuel Tank Volume: 0.47 L (16 fl. oz.)
Sound Pressure Level: Approx. 94 dB(A)
Vibration Level (left/right): Approx. 4.5/6.5 m/s²

Note: Specifications subject to change. Refer to engine housing or official STIHL documentation for exact model details.