STIHL HS 45 Service Manual

The STIHL HS 45 is a professional-grade hedge trimmer designed for demanding use. This manual provides essential information for servicing, maintenance, troubleshooting, and safe operation of the HS 45 model. It covers specifications, disassembly and assembly procedures, fuel system, ignition system, cutting attachment, and important safety warnings. Always refer to this manual before performing any service work.

1. Safety Instructions 2. Specifications 3. Maintenance Schedule 4. Fuel System Service 5. Ignition System 6. Cutting Attachment 7. Carburetor Adjustment 8. Disassembly & Assembly 9. Troubleshooting 10. Parts List 11. Warranty & Support

Safety Instructions

Before servicing, read all safety warnings. Use proper personal protective equipment (PPE).

Hazard	Precaution
Fuel Fire/Explosion	Work in well-ventilated area away from sparks or flames. Use approved fuel containers.
Sharp Blades	Always wear cut-resistant gloves. Ensure the engine is off and spark plug disconnected.
Hot Surfaces	Allow engine and muffler to cool completely before handling.
Toxic Fumes	Do not run engine indoors. Service in a ventilated space.
Electrical Shock	Disconnect spark plug wire before working on ignition or cutting system.

Specifications

Model: STIHL HS 45
Engine Type: 2-stroke, single-cylinder, air-cooled
Displacement: 27.2 cm³
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 (without cutter bar): 5.2 kg (11.5 lbs)
Ignition System: Electronic, breakerless
Carburetor: Membrane carburetor

Maintenance Schedule

Follow this schedule to ensure optimal performance and longevity.

Before Each Use: Check for loose fasteners, fuel leaks, and cutter blade condition.
Every 10 Hours: Clean air filter, check spark plug.
Every 20 Hours: Clean cooling fins, check fuel filter, lubricate cutter bar.
Every 50 Hours: Clean spark arrestor screen (if equipped), check carburetor settings.
Every 100 Hours: Replace fuel filter, inspect ignition system.
Annually: Full service: Clean carburetor, check all gaskets and seals.

WARNING! Use only genuine STIHL replacement parts. Incorrect parts can cause failure or injury.

Fuel System Service

Components: Fuel tank, fuel filter, fuel lines, carburetor.

Fuel Tank: Drain old fuel. Inspect for cracks or leaks.
Fuel Filter: Replace if clogged. Pull from tank using a wire hook.
Fuel Lines: Check for brittleness or cracks. Replace if damaged.
Carburetor: Clean jets and membranes. Adjust idle and high-speed screws per specifications.

CAUTION! Fuel is highly flammable. No smoking during service.

Ignition System

Electronic ignition module, spark plug, stop switch.

Spark Plug: Type BOSCH WSR 6 F or equivalent. Gap: 0.5 mm (0.020 in).
Testing: Check for spark by grounding plug against cylinder. No spark indicates faulty module or wire.
Ignition Module: Resistance check: Primary 1.5-2.5 Ω, Secondary 8-12 kΩ. Replace if out of spec.
Stop Switch: Ensure wire is intact and switch functions correctly.

Cutting Attachment

Double-sided reciprocating blades, gear drive, lubrication points.

Blade Removal: Remove blade bolts. Carefully slide blade off drive pins.
Cleaning: Remove sap and debris with a plastic scraper and solvent.
Sharpening: Use a flat file. Maintain original tooth angle. Do not overheat.
Lubrication: Apply STIHL hedge trimmer oil to both sides of blade before and during use.
Reassembly: Ensure blade moves freely without binding. Torque bolts to 8-10 Nm (70-88 in-lb).

Tip: A dull blade increases load on the engine. Keep it sharp.

Carburetor Adjustment

Adjust with engine at operating temperature. Use a tachometer for accuracy.

Screw	Function	Preliminary Setting
L (Low Speed)	Idle mixture	Turn in gently to seat, then open 1 turn
H (High Speed)	High-speed mixture	Turn in gently to seat, then open 1 turn
LA (Idle Speed)	Engine idle RPM	Adjust to achieve 2800-3200 RPM at idle

Procedure: Start engine. Warm up for 5 minutes. Adjust L screw for smoothest idle. Adjust H screw for maximum RPM, then rich slightly. Set LA for stable idle. Re-check after load test.

Disassembly & Assembly

Major steps for engine access. Refer to detailed diagrams in parts list.

Remove cutting attachment and top handle cover.
Remove fuel tank and air filter cover.
Disconnect throttle linkage and choke rod.
Remove cylinder cover and muffler.
Remove cylinder bolts and carefully lift cylinder.
Inspect piston, rings, and cylinder for scoring.
Assembly: Reverse order. Use new gaskets. Torque cylinder bolts to 10 Nm (88 in-lb) in crisscross pattern.

WARNING! Mark all connections and take photos during disassembly to aid reassembly.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, old fuel, clogged carburetor	Check spark, replace fuel, clean carburetor jets.
Engine runs poorly/ lacks power	Dirty air filter, incorrect carb adjustment, clogged spark arrestor	Clean/replace filter, adjust carburetor, clean spark arrestor screen.
Excessive vibration	Loose fasteners, unbalanced/damaged blade, worn anti-vibration mounts	Tighten all bolts, inspect/replace blade, check mounts.
Blade does not move	Sheared drive pin, seized gearbox, clutch failure	Inspect drive pins and gearbox. Replace damaged parts.
Engine overheats	Dirty cooling fins, lean fuel mixture, low oil in fuel	Clean fins, adjust carburetor richer, ensure correct fuel/oil mix.

Parts List

Key replacement part numbers (consult official STIHL catalog for complete list).

Spark Plug: BOSCH WSR 6 F / STIHL 0000 400 1300
Air Filter: STIHL 0000 120 1605
Fuel Filter: STIHL 0000 350 3501
Carburetor Kit: STIHL 0000 350 0700
Cutter Blade Set: STIHL 4135 713 0601
Ignition Module: STIHL 0000 400 1305
Piston Ring Set: STIHL 0000 030 2003

Warranty & Support

STIHL Limited Warranty applies to original purchaser. Service by an authorized STIHL servicing dealer is recommended for warranty claims.

For Technical Support: Contact your local authorized STIHL dealer.

Online Resources: Visit www.stihlusa.com for manuals, safety videos, and dealer locator.

Phone: STIHL USA Customer Service: 1-800-467-8445

Important: This manual is for reference only. STIHL reserves the right to make changes. Always prioritize safety.