Stihl FS 38 User Manual

The Stihl FS 38 is a lightweight, easy-to-handle gasoline-powered string trimmer designed for residential lawn and garden maintenance. It features a reliable 2-stroke engine, a straight shaft, a loop handle for comfortable operation, a Tap Advance™ cutting head for easy line feed, and a debris shield for operator protection. 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 Advance™ cutting head, Debris shield, Throttle trigger with lockout, Stop switch.

Feature	Description
Engine	27.2 cc 2-stroke, air-cooled gasoline engine
Powerhead	Integrated fuel tank and engine housing
Shaft	Straight solid drive shaft
Handle	Loop handle with vibration damping
Cutting Head	Tap Advance™ bump feed trimmer head
Debris Shield	Protects operator from thrown debris
Throttle Trigger	With lockout to prevent accidental operation
Stop Switch	Easy-access engine stop switch
Fuel Tank	Integrated, 0.95 pint (0.45 liter) capacity
Weight	Approximately 10.1 lbs (4.6 kg) without fuel

Assembly & Preparation

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

1. Attach the handle: Align handle with shaft and secure with provided bolts.
2. Install the debris shield: Slide onto shaft and secure according to instructions.
3. Install the cutting head: Thread the Tap Advance™ head onto the drive shaft (counter-clockwise to tighten).
4. Fill the trimmer line: Wind recommended line onto spool and install into head.

WARNING! Do not assemble or fuel the unit near open flames or sparks. Wear protective gloves.

First-Time Operation

Before starting, ensure proper fuel mix is in tank and all guards are installed.

1. Fueling: Use fresh fuel mix (50:1 gasoline to 2-stroke oil). Fill to marked level.
2. Starting Procedure: Place unit on flat ground. Set stop switch to "I". Press fuel primer bulb 5 times. Set choke lever to cold start position. Pull starter rope briskly until engine fires. Move choke to run position. Pull starter rope again to start.
3. Warm-up: Allow engine to run at idle for 30 seconds before applying throttle.

CAUTION! Keep bystanders, pets, and children at least 50 feet away during operation.

Specifications

• Engine Displacement: 27.2 cc.
• Engine Type: 2-stroke, single cylinder, air-cooled.
• Fuel/Oil Ratio: 50:1 (Stihl HP Ultra oil or equivalent).
• Fuel Tank Capacity: 0.95 US pint (0.45 liter).
• Drive Shaft: Straight solid shaft.
• Cutting Width: Approx. 16 inches with standard line.
• Sound Power Level: 100 dB(A) (measured per standard).
• Vibration Levels: Front handle: < 2.5 m/s², Rear handle: < 2.5 m/s².
• Warranty: Limited warranty for residential use.

Controls and Settings

Main controls located on the handle and powerhead.

Handle Area: Throttle trigger with lockout, Stop switch (I/O).

Powerhead: Choke lever (cold start/run), Fuel primer bulb, Fuel tank cap, Starter grip.

Adjustments: Handle can be rotated for user comfort. Shoulder strap attachment points provided.

Fuel & Oil Mixing

Use only fresh, unleaded gasoline with a minimum octane rating of 89. Mix with a high-quality 2-stroke engine oil at a 50:1 ratio.

1. Use an approved mixing container.
2. Add correct amount of oil first, then gasoline.
3. Close container and shake thoroughly.
4. Fill fuel tank. Clean any spilled fuel immediately.

Tip: Use Stihl HP Ultra oil for best performance and reduced carbon deposits. Never use automotive oil or oil intended for 4-stroke engines.

Cutting Techniques

For effective and safe trimming.

1. Hold the trimmer with both hands, right hand on throttle handle, left hand on loop handle.
2. Keep the cutting head parallel to the ground and use a sweeping side-to-side motion.
3. Advance line: Lightly tap the cutting head on the ground while at high RPM to feed new line.
4. Avoid cutting near hard objects like fences, rocks, or tree trunks to prevent line wear and kickback.
5. For edging, tilt the trimmer so the cutting line is vertical.

WARNING! Always wear eye protection, hearing protection, long pants, and sturdy shoes. Never operate with damaged guards or shields.

Maintenance Schedule

Regular maintenance ensures long life and safe operation.

Task	Frequency
Check/clean air filter	Every 10 operating hours
Check spark plug	Every 25 operating hours
Clean spark arrestor screen (if equipped)	Every 50 operating hours
Check fuel filter	Every season or as needed
Clean cooling fins	Every season
Grease drive shaft	Every 100 operating hours
Inspect cutting head and line	Before each use

Storage

For storage periods longer than 30 days.

1. Drain all fuel from the tank and carburetor by running the engine until it stops.
2. Remove spark plug and add a teaspoon of engine oil into the cylinder. Pull starter rope slowly to distribute oil, then reinstall plug.
3. Clean the entire unit thoroughly.
4. Store in a dry, cool, and well-ventilated place, out of reach of children.

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

Safety Information

Read and understand all instructions before use.

• Always wear appropriate Personal Protective Equipment (PPE): safety glasses, hearing protection, gloves, long pants, and sturdy boots.
• Inspect the unit before each use. Do not operate if damaged, leaking, or if guards are missing.
• Clear the work area of stones, sticks, wire, and other debris.
• Keep all bystanders at a safe distance.
• Operate only in good daylight and visibility.
• Never operate the unit when you are tired, ill, or under the influence of alcohol or drugs.
• Use the shoulder strap for better control and reduced fatigue.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, spark plug faulty	Check fuel level. Set choke to run, hold throttle open, pull starter. Check/replace spark plug.
Engine starts but dies	Clogged fuel filter, dirty air filter	Replace fuel filter. Clean or replace air filter.
Loss of power	Clogged air filter, old fuel	Clean air filter. Drain and replace with fresh fuel mix.
Line does not advance	Line tangled, head worn	Disassemble head and rewind line. Replace spool if worn.
Excessive vibration	Damaged cutting head, loose parts	Inspect head for damage. Tighten all bolts and handles.

Service: For repairs not covered in this manual, contact an authorized Stihl servicing dealer.

Support: Visit www.stihlusa.com or contact your local Stihl dealer.