Stihl HS 45 Repair Manual

The Stihl HS 45 is a professional-grade hedge trimmer designed for demanding use. This manual provides comprehensive repair, maintenance, and troubleshooting guidance for the HS 45 model, covering the engine, cutting system, fuel system, ignition, and safety components. Below are key sections for safety, specifications, disassembly, troubleshooting, and maintenance procedures.

1. Safety Precautions 2. Technical Specifications 3. Tools Required 4. Engine System Repair 5. Cutting System Repair 6. Fuel System Repair 7. Ignition System Repair 8. Carburetor Adjustment 9. Common Fault Diagnosis 10. Maintenance Schedule 11. Parts List & Diagrams

Safety Precautions

Before performing any repair, ensure the hedge trimmer is turned off, the spark plug boot is disconnected, and all moving parts have stopped completely.

Precaution	Description
Disconnect Spark Plug	Prevents accidental engine start during repair
Wear Protective Gear	Use gloves and safety glasses
Work in Well-Ventilated Area	Avoid inhalation of fuel vapors
Secure the Tool	Clamp or secure the unit to prevent movement
Use Genuine Parts	Ensure compatibility and safety

Technical Specifications

Model: Stihl HS 45
Engine Type: 2-stroke, single-cylinder, air-cooled
Displacement: 27.2 cc
Power Output: 0.8 kW (1.1 hp)
Fuel/Oil Mix: 50:1 (Stihl HP Ultra or equivalent)
Cutting Length: 60 cm (24 inches)
Tooth Spacing: 20 mm
Weight: 4.9 kg (10.8 lbs)
Ignition System: Electronic, capacitor discharge

Tools Required

Standard and Stihl-specific tools needed for repair.

Spark plug wrench
T-wrench set (Torx T27, T20)
Screwdriver set (flathead, Phillips)
Feeler gauge set
Carburetor adjustment tool
Compression tester
Stihl special tool for clutch removal (if needed)

WARNING! Use correct tools to avoid damage to components.

Engine System Repair

Procedures for cylinder, piston, crankshaft, and bearings.

Cylinder & Piston Inspection: Remove muffler, inspect for scoring, carbon buildup.
Piston Ring Replacement: Remove circlips, piston pin, replace rings with correct orientation.
Crankshaft Seal Replacement: Remove clutch/flywheel, pry out old seals, press in new seals.
Compression Check: Should be above 100 psi (6.9 bar).

CAUTION! Label parts during disassembly for correct reassembly.

Cutting System Repair

Blade maintenance, gear drive, and lubrication.

Blade Removal: Remove blade bolts, separate upper and lower blades.
Blade Sharpening: Use flat file, maintain original angle, deburr edges.
Gear Drive Inspection: Check drive gear and pinion for wear, replace if teeth are damaged.
Lubrication: Apply Stihl hedge trimmer grease to gear teeth and blade surfaces.

Tip: Clean blades with solvent to remove sap and debris before sharpening.

Fuel System Repair

Fuel tank, lines, filter, and carburetor.

Fuel Line Replacement: Drain tank, remove old lines, install new lines with correct routing.
Fuel Filter Replacement: Replace in-tank filter annually or when clogged.
Tank Vent Check: Ensure vent is not blocked; clean or replace if necessary.
Carburetor Removal: Disconnect linkages, fuel line, and mounting bolts.

WARNING! Ensure fuel system is completely drained before repair to prevent fire.

Ignition System Repair

Spark plug, ignition module, and stop switch.

Spark Plug: Gap 0.5 mm (0.020 in), replace if electrode is worn.
Ignition Module Test: Check for spark with tester; replace module if no spark.
Stop Switch Wire: Test continuity; wire should break circuit when switch is pressed.
Flywheel Key: Inspect for shearing; replace if damaged to maintain timing.

Carburetor Adjustment

Standard settings and fine-tuning procedure.

Screw	Initial Setting	Function
L (Low Speed)	1 turn open	Idle and low-speed mixture
H (High Speed)	1 turn open	High-speed mixture
LA (Idle Speed)	Set for smooth idle	Idle speed adjustment

Fine-tune at operating temperature: Adjust L for smooth acceleration, H for maximum RPM without leaning out.

Common Fault Diagnosis

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, fuel issue, flooded	Check spark, fuel flow, dry plug.
Engine runs poorly	Dirty air filter, clogged fuel filter, carb adjustment	Clean/replace filters, adjust carb.
Excessive vibration	Damaged blade, loose bolts, worn bearings	Inspect blade, tighten bolts, check bearings.
Loss of power	Clogged muffler, carbon buildup, compression loss	Clean muffler, decarbonize, check compression.
Blades not moving	Sheared drive gear, clutch issue, broken linkage	Inspect gear drive, clutch, linkage.

Maintenance Schedule

Daily: Clean air filter, check blade condition.
Every 25 hours: Clean spark arrestor screen, check fuel filter.
Every 50 hours: Replace spark plug, grease gear drive.
Every 100 hours: Check compression, replace fuel lines.
Annually: Full carburetor service, inspect crankshaft seals.

CAUTION! Adhere to schedule for optimal performance and safety.

Parts List & Diagrams

Refer to official Stihl parts catalog for HS 45 (Part No. 0000 350 3205). Key components include:

Cylinder & Piston Assembly
Carburetor (Zama C1Q-S267)
Ignition Module
Clutch Assembly
Gear Housing & Blades
Fuel Tank Assembly

Ordering: Use Stihl dealer or online parts system with model and serial number.

Support: Contact Stihl authorized service center or visit www.stihlusa.com.