Stihl FS 450 Manual

The Stihl FS 450 is a professional-grade, high-performance brushcutter/string trimmer designed for demanding clearing and maintenance work. It features a powerful 2-stroke engine with electronic ignition, anti-vibration system, ErgoStart, and a comprehensive safety system. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Powerful 2-stroke engine, ErgoStart system, anti-vibration handles, quick-release harness, and compatible with a wide range of cutting heads and blades.

Feature	Description
Engine Type	2-stroke, single-cylinder, air-cooled
Displacement	45.6 cc
Power Output	High performance for professional use
Ignition System	Electronic, CDI
Starting System	ErgoStart for easy pull starts
Anti-Vibration	Advanced system in handles and shaft
Fuel System	Diaphragm carburetor with purge bulb
Drive Shaft	Solid, heavy-duty
Cutting Attachment	Accepts trimmer heads and metal blades
Harness	Quick-release professional harness included

Safety Information

Read and understand all instructions before operation. Always wear appropriate PPE.

1. Personal Protective Equipment (PPE): Wear safety glasses, hearing protection, gloves, long pants, and sturdy boots.
2. Clear Work Area: Remove stones, nails, wire, and other debris that could be thrown.
3. Fuel Safety: Refuel outdoors only, with engine stopped and cool. Use approved fuel container.
4. Operation: Keep bystanders and pets at least 50 feet away. Hold unit firmly with both hands.
5. Transport: Secure unit during transport. Carry by handles with cutting attachment covered.

WARNING! Risk of severe injury or death from blade contact or thrown objects. Never operate without proper guards and PPE.

Assembly & First Use

Unpack and inspect all parts. Assemble according to instructions.

1. Attach Handle: Secure handle to shaft at desired position using provided bolts.
2. Install Harness: Attach harness loops to mounting points on the unit.
3. Install Cutting Attachment: Ensure engine is off. Attach trimmer head or blade, securing with retaining nut and guard.
4. Fuel Mix: Use only high-quality 2-stroke engine oil mixed with unleaded gasoline at a 50:1 ratio (STIHL HP Ultra oil recommended).
5. Starting: Place unit on clear ground. Set master control lever to cold start position. Pull starter rope until engine fires.

CAUTION! Ensure all fasteners are tight before operation. Do not force components during assembly.

Specifications

• Engine Displacement: 45.6 cc
• Powerhead Weight: Approximately 12.1 lbs (without cutting attachment)
• Fuel Tank Capacity: 24.3 fl oz
• Oil Tank Capacity: Integrated oilomatic system for certain cutting heads
• Sound Pressure Level: High - hearing protection required
• Vibration Levels: Reduced via anti-vibration system
• Drive System: Solid shaft with gearhead
• Recommended Fuel: Unleaded gasoline (min 89 octane) with STIHL 2-stroke oil
• Warranty: Limited commercial warranty (see manual)

Controls and Functions

Master Control Lever: Combines stop switch, choke, and run positions. Throttle Trigger: Located on rear handle. Throttle Trigger Lockout: Must be depressed to engage throttle. Decompression Valve: Reduces pulling force for starting. Purge Bulb: Press to prime carburetor before cold start.

Starting Sequence: 1. Press purge bulb 5-10 times. 2. Set master control to cold start (choke). 3. Pull starter rope sharply until engine fires. 4. Move master control to run position. 5. Pull starter rope to start engine.

Operation

Always operate with proper stance and harness adjustment.

1. Harness: Adjust straps so unit hangs comfortably with cutting head off the ground.
2. Starting: Follow starting sequence. Warm up engine for 30 seconds before applying load.
3. Cutting Technique: Use a smooth, sweeping motion from right to left. Do not force the tool.
4. Shut Down: Release throttle, allow engine to idle for 30 seconds, then move master control to STOP.
5. Refueling: Stop engine and allow to cool. Clean area around fuel cap. Refill with proper fuel mix.

Tip: For heavy brush, use a metal blade. For grass and light weeds, use a trimmer head with line.

Maintenance Schedule

Regular maintenance ensures performance and longevity.

Interval	Task
Before each use	Check for loose fasteners, damaged parts, fuel leaks. Inspect cutting attachment.
Daily	Clean air filter. Check spark plug condition.
Every 50 hours	Clean spark arrestor screen (if equipped). Check fuel filter.
Every 100 hours	Replace spark plug. Clean carburetor air intake.
Annually	Have unit serviced by an authorized STIHL dealer.

WARNING! Perform maintenance only when engine is off and cool. Disconnect spark plug wire for safety.

Cutting Attachments

Compatible with various STIHL trimmer heads and circular blades.

1. Trimmer Heads: AutoCut, PolyCut heads for nylon line. Ensure correct line diameter and length.
2. Metal Blades: Circular saw blades for clearing brush and small saplings. Always use correct guard.
3. Installation: Use appropriate wrench to secure. Ensure cutting direction arrow matches blade rotation.
4. Sharpening: Keep blades sharp. Dull blades reduce efficiency and increase load on engine.

CAUTION! Never use damaged blades or heads. Ensure guard is properly installed for each attachment.

Storage

Prepare unit for storage if not used for more than 30 days.

1. Fuel System: Run engine until it stops to empty carburetor. Or, add fuel stabilizer to full tank and run for 5 minutes.
2. Cleaning: Clean exterior of debris. Wipe down with dry cloth.
3. Storage Location: Store in a dry, secure place, out of reach of children.
4. Battery (if equipped): Remove and store separately in a cool, dry place.

CAUTION! Storing with untreated fuel can cause carburetor damage. Always follow fuel stabilization procedures.

Warranty & Compliance

STIHL Limited Warranty: Covers defects in materials and workmanship for commercial use; period varies by region. EPA & CARB: Meets emission standards for handheld engines. Noise Compliance: Meets applicable sound power level directives. For genuine parts and service, contact an authorized STIHL dealer. For support, visit www.stihlusa.com or contact 1-800-467-8445.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel, flooded, bad spark	Check fuel level. Move master control to run, pull starter 10x to clear flood. Check spark plug.
Engine starts then dies	Clogged fuel filter, dirty air filter	Replace fuel filter. Clean or replace air filter.
Loss of power	Clogged spark arrestor, dirty carburetor	Clean spark arrestor screen. Have carburetor serviced.
Excessive vibration	Damaged cutting attachment, loose parts	Inspect blade/head for damage. Tighten all fasteners.
Cutting attachment does not spin	Broken drive shaft, clutch issue	Stop engine. Inspect for visible damage. Contact STIHL dealer.

Dealer Service: For complex repairs, take to an authorized STIHL dealer.

Support: 1-800-467-8445; www.stihlusa.com