Stihl FS44 Repair Manual

The Stihl FS44 is a lightweight, versatile string trimmer designed for residential use. This repair manual covers essential maintenance, troubleshooting, and repair procedures for the FS44 model, including engine components, fuel system, ignition system, cutting head, and safety features. Below are key sections for safety precautions, specifications, maintenance schedules, troubleshooting, and step-by-step repair instructions.

Safety Precautions

Always prioritize safety when performing repairs. Wear appropriate personal protective equipment (PPE) and work in a well-ventilated area.

Precaution	Description
Disconnect spark plug	Always disconnect spark plug wire before starting any repair to prevent accidental starting.
Use proper tools	Use Stihl-approved tools or equivalents to avoid damage to components.
Fuel safety	Drain fuel tank before repairs; work away from open flames or sparks.
Sharp components	Handle cutting head and blades with care; wear cut-resistant gloves.
Clean work area	Keep area free of debris and flammable materials.
Follow torque specs	Use torque wrench for critical fasteners to prevent over-tightening or stripping.
Replace damaged parts	Do not attempt to repair cracked or worn parts; replace with genuine Stihl parts.
Battery safety	If equipped with electric start, disconnect battery before servicing electrical components.
Eye protection	Always wear safety glasses or goggles when performing repairs.
Manual reference	Refer to this manual and official Stihl documentation for specific procedures.

Specifications

Technical specifications for the Stihl FS44 string trimmer.

• Engine Type: 2-stroke, single-cylinder, air-cooled.
• Displacement: 27.2 cc (1.66 cu in).
• Power Output: 0.8 kW (1.1 hp).
• Fuel/Oil Mix: 50:1 (Stihl HP Ultra oil recommended).
• Fuel Tank Capacity: 0.47 liters (16 oz).
• Cutting Width: Up to 43 cm (17 inches) with optional blades.
• Drive System: Flexible drive shaft with gearhead.
• Cutting Attachment: Tap-and-Go cutting head (standard), optional blades available.
• Weight: Approximately 4.9 kg (10.8 lbs) without cutting attachment.
• Sound Pressure Level: 96 dB(A) typical at operator's ear.
• Vibration Level: Front handle: 4.5 m/s²; Rear handle: 6.5 m/s².

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity. Follow this schedule based on hours of operation or time intervals.

1. Before Each Use: Check for loose fasteners, inspect cutting attachment, ensure throttle trigger moves freely.
2. Every 10 Hours: Clean air filter, check spark plug condition, inspect fuel filter.
3. Every 25 Hours: Replace air filter, clean spark arrestor screen (if equipped), check drive shaft lubrication.
4. Every 50 Hours: Replace spark plug, clean carburetor (external), check fuel lines for cracks.
5. Every 100 Hours: Replace fuel filter, clean carburetor (internal), inspect clutch and gearhead.
6. Seasonal: Drain fuel for storage, lubricate cutting head bearings, inspect entire unit for wear.

WARNING! Never use automotive oil or non-recommended lubricants. Use only Stihl-approved fluids and parts.

Engine Components

Key engine parts: Cylinder, piston, crankshaft, carburetor, ignition module.

Carburetor Adjustment: Use tachometer for idle (2800-3200 RPM) and high-speed (12,500-13,500 RPM) settings. Adjust LA (idle) and H (high) screws carefully.

Piston/Cylinder Inspection: Remove muffler to inspect piston through exhaust port. Look for scoring or carbon buildup. Cylinder should be smooth; replace if scratched.

Ignition Module: Check for spark with tester; gap should be 0.5 mm. Replace if no spark and spark plug is confirmed good.

Fuel System

Components: Fuel tank, filter, lines, carburetor (Walbro or Zama).

1. Drain fuel: Use siphon or tilt unit to empty tank.
2. Replace fuel filter: Disconnect line, insert new filter into tank.
3. Inspect fuel lines: Check for cracks, stiffness, or leaks; replace if damaged.
4. Carburetor cleaning: Remove, disassemble, clean with carburetor cleaner, replace diaphragm and gaskets if worn.

Tip: Always use fresh fuel mix (less than 30 days old) to prevent carburetor issues.

Ignition System

Components: Spark plug (Bosch WSR6F or equivalent), ignition module, stop switch, wiring.

1. Spark plug: Remove, check electrode gap (0.5 mm), clean or replace if fouled.
2. Ignition test: Use spark tester; if no spark, check stop switch continuity and wiring.
3. Module replacement: Remove flywheel (use puller), replace module, set air gap (0.3 mm) with feeler gauge.
4. Flywheel key: Inspect for shearing; replace if damaged to maintain timing.

WARNING! Do not crank engine with spark plug removed and wire grounded to cylinder—can damage ignition module.

Cutting Head & Drive Shaft

Cutting Head: Tap-and-Go system for easy line advance. Drive Shaft: Flexible steel cable inside shaft tube.

1. Head removal: Press locking tabs, twist counterclockwise to remove.
2. Line replacement: Wind 2.0 mm diameter line onto spool in direction of arrows.
3. Drive shaft lubrication: Disconnect shaft from engine, apply Stihl grease to splines.
4. Gearhead inspection: Check for worn gears or bearings; replace if noisy or stiff.
5. Shaft alignment: Ensure straightness; bent shafts cause vibration and must be replaced.

CAUTION! Always wear gloves when handling cutting line or blades.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, fuel issues, flooded	Check spark plug, fuel freshness, carburetor; dry plug if flooded.
Engine starts then dies	Clogged fuel filter, carburetor adjustment	Replace fuel filter; adjust carburetor idle screw.
Loss of power	Dirty air filter, exhaust screen clogged	Clean/replace air filter; clean spark arrestor screen.
Excessive vibration	Bent drive shaft, unbalanced cutting head	Inspect shaft for bends; replace head if damaged.
Line not advancing	Worn spool, tangled line	Replace spool; rewind line correctly.
Overheating	Lean fuel mix, clogged cooling fins	Adjust carburetor; clean cylinder cooling fins.
Clutch slipping	Worn clutch shoes, weak springs	Replace clutch assembly.
Gearhead noise	Lack of lubrication, worn gears	Lubricate with gear grease; replace gear set if necessary.

Reset: For electronic ignition issues, disconnect spark plug wire for 1 minute to reset module.

Disassembly & Assembly

General steps for major repairs. Refer to diagrams for specific part locations.

1. Remove cutting attachment: Lock shaft, unscrew gearhead.
2. Separate shaft from engine: Remove bolts at engine coupling.
3. Engine disassembly: Remove starter assembly, fan housing, cylinder cover.
4. Piston/cylinder removal: Remove cylinder base nuts, lift cylinder carefully.
5. Carburetor removal: Disconnect fuel lines, remove mounting nuts.
6. Reassembly: Reverse order, use new gaskets, torque fasteners to spec.

Torque Specifications: Cylinder nuts: 10 Nm (88 in-lb), Fan housing screws: 3 Nm (27 in-lb), Gearhead bolts: 15 Nm (11 ft-lb).

Parts List & Diagrams

Key replacement parts (genuine Stihl numbers):

• Air Filter: 0000 120 1620
• Spark Plug: 0000 400 1300 (Bosch WSR6F)
• Fuel Filter: 0000 350 3501
• Carburetor Kit: 0000 120 0650 (includes diaphragm, gaskets)
• Cutting Head Spool: 0000 160 2021
• Drive Shaft: 4130 160 2005
• Ignition Module: 0000 400 1305
• Clutch Assembly: 0000 160 4100

Diagrams: Refer to official Stihl FS44 parts diagrams for exploded views and part locations (available at stihlusa.com or authorized dealers).

Warranty & Support

Stihl Limited Warranty: 1 year commercial use, 2 year residential use from date of purchase. Keep original receipt.

Service Centers: Authorized Stihl dealers provide repairs and genuine parts. Use dealer locator at www.stihlusa.com.

Technical Support: Contact Stihl customer service at 1-800-467-8445 or [email protected] for manual requests or technical questions.

Safety Recall Information: Check stihl.com for any recalls or safety notices related to FS44.

Manual Updates: Latest version of this repair manual available for download at stihl.com under manuals section.