Stihl FS 38 Trimmer Manual

The Stihl FS 38 is a lightweight, easy-to-handle gasoline-powered grass trimmer designed for residential use. It features a curved shaft, a reliable 2-stroke engine with a single-lever master control, a semi-automatic choke, a translucent fuel tank, a Tapmatic™ automatic oiler for the cutting head, and a loop handle with vibration damping. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Safety Information 3. Assembly & Preparation 4. Specifications 5. Controls and Starting 6. Operation & Techniques 7. Maintenance Schedule 8. Storage 9. Warranty Information 10. Troubleshooting

Features at a Glance

Key components: 2-stroke engine, Curved shaft, Loop handle, Translucent fuel tank, Tapmatic™ automatic line feed, Cutting head guard.

Feature	Description
Engine	27.2 cc 2-stroke, air-cooled gasoline engine
Shaft	Curved, lightweight design for easy handling
Master Control Lever	Single lever for choke, stop, and run functions
Fuel Tank	Translucent for easy fuel level checking
Cutting Attachment	Tapmatic™ automatic bump-feed cutting head (line)
Handle	Loop handle with integrated vibration damping
Starter	Rewind starter with ElastoStart for reduced pull force
Throttle Trigger	With throttle trigger lockout for safety
Spark Plug	Bosch or NGK type, easily accessible
Exhaust	Muffler with integrated spark arresting screen

Safety Information

Read and understand all instructions before use. Wear appropriate PPE.

Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, long pants, sturdy boots, and gloves.
Clear Work Area: Remove stones, sticks, wire, and other debris before trimming.
Fuel Safety: Refuel outdoors, with engine off and cool. Use clean gasoline and Stihl 2-stroke oil at 50:1 ratio.
Operation: Keep bystanders and pets at least 50 feet away. Hold unit firmly with both hands.

WARNING! Risk of serious injury or death from rotating cutting line, thrown objects, fire, or carbon monoxide. Operate with extreme caution.

Assembly & Preparation

Assemble the trimmer before first use.

Attach the handle: Slide onto shaft, align, and tighten screws.
Install the cutting guard: Align with mounting holes on gearhead and secure.
Install the cutting head: Thread onto drive shaft and tighten securely by hand.
Fill with fuel: Mix Stihl 2-stroke oil with unleaded gasoline (min. 89 octane) at a 50:1 ratio. Fill tank.
Fill with line: Wind .095" diameter nylon line onto spool and install into cutting head.

CAUTION! Ensure all fasteners are tight. Do not operate without cutting guard installed.

Specifications

Engine Displacement: 27.2 cc
Power Output: 0.9 kW (1.2 bhp)
Fuel/Oil Ratio: 50:1 (Stihl 2-Stroke Oil)
Fuel Tank Capacity: 14.9 fl. oz. (0.44 liters)
Idle Speed: 2,800 rpm
Maximum Powerhead Speed: 11,500 rpm
Drive System: Flexible drive shaft
Cutting Swath: Approx. 16 inches (with line head)
Weight (powerhead): 9.9 lbs (4.5 kg)
Sound Pressure Level: Approx. 96 dB(A)
Vibration Level (left/right): Approx. 4.5/6.5 m/s²

Controls and Starting

Master Control Lever Positions: STOP (0), CHOKE (up), RUN (down). Throttle trigger with lockout.

Cold Start Procedure:

Press fuel primer bulb 5-10 times until fuel is visible.
Set Master Control lever to CHOKE position (up).
While holding unit firmly on ground, pull starter rope briskly 2-3 times until engine 'pops'.
Move Master Control lever to RUN position (down).
Pull starter rope again to start engine.
Allow engine to warm up at idle for 30 seconds.

Warm Start: Set lever to RUN and pull starter.

Stopping: Move Master Control lever to STOP (0).

Operation & Techniques

Hold trimmer with right hand on throttle handle, left hand on loop handle. Maintain secure footing.

Basic Trimming: Swing trimmer in an arc from right to left, keeping cutting head parallel to ground.
Edging: Tilt trimmer so cutting line is vertical along sidewalk or driveway edge.
Line Advance: Bump cutting head firmly on ground (with engine at high speed) to feed fresh line.
Avoiding Damage: Do not force cutting head into dense material. Do not use for woody brush.

Tip: Work in a systematic pattern, overlapping swings slightly for even cutting.

Maintenance Schedule

Perform regular maintenance for optimal performance and longevity.

Interval	Task
Before each use	Check for loose fasteners, damaged parts, fuel level.
Every 25 hours	Clean air filter (replace if damaged). Check spark plug.
Every 50 hours	Clean spark arrestor screen in muffler. Check fuel filter.
Seasonally/Annually	Replace spark plug. Clean cooling fins. Inspect drive shaft.
As needed	Refill line spool. Replace worn cutting guard.

CAUTION! Always disconnect spark plug boot before performing maintenance.

Storage

Prepare trimmer for storage if not in use for more than 30 days.

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

WARNING! Never store unit with fuel in the tank in an enclosed area. Fuel vapors can ignite.

Warranty Information

Stihl FS 38 includes a limited warranty for residential use. Warranty period and terms vary by region. Proof of purchase from an authorized Stihl dealer is required. Warranty does not cover damage from misuse, neglect, improper fuel, or unauthorized repairs. For warranty service, contact the authorized Stihl dealer where the unit was purchased.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, spark plug faulty	Check fuel; set lever to RUN and pull with throttle open (if flooded); check/clean/replace spark plug.
Engine starts then dies	Clogged air filter, fuel filter, or carburetor	Clean or replace air filter. Check fuel line and filter. May need carburetor adjustment.
Loss of power	Dirty air filter, clogged spark arrestor	Clean air filter. Clean spark arrestor screen in muffler.
Excessive vibration	Bent drive shaft, loose parts, unbalanced cutting head	Inspect shaft for damage. Tighten all fasteners. Ensure line is wound evenly.
Line does not feed	Empty spool, tangled line, worn bump head	Refill spool with correct line. Clear tangles. Replace bump head if worn.
Engine overheats	Dirty cooling fins, lean fuel mixture	Clean cooling fins. Ensure correct 50:1 fuel mix. Check for air leaks.

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

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