STIHL FS45C Owner's Manual

The STIHL FS45C is a lightweight, straight-shaft grass trimmer designed for residential use. It features a 2-stroke engine with a displacement of 27.2 cc, a loop handle for comfortable operation, a Tap'N'Go™ semi-automatic cutting head line advance system, a PolyCut™ head for reduced line wear, and a debris shield. This manual covers safety, assembly, operation, maintenance, troubleshooting, and specifications. Always read and understand the manual before use.

Features at a Glance

Key components: 2-stroke engine, straight shaft, loop handle, Tap'N'Go™ cutting head, debris shield, throttle trigger lockout, and stop switch.

Feature	Description
Engine	27.2 cc 2-stroke, air-cooled
Shaft	Straight, solid drive shaft
Handle	Loop handle with vibration damping
Cutting Head	Tap'N'Go™ semi-automatic line advance
Cutting Attachment	PolyCut™ head with 0.095" (2.4 mm) line
Debris Shield	Protects operator from debris
Throttle Trigger Lockout	Prevents accidental throttle engagement
Stop Switch	Stops engine immediately
Fuel Tank Capacity	Approx. 13.5 fl oz (0.4 liters)
Weight (dry)	Approx. 10.1 lbs (4.6 kg)

Safety Information

Read and follow all safety instructions to prevent serious injury or death.

1. Personal Protective Equipment (PPE): Always wear eye protection, hearing protection, long pants, sturdy boots, and gloves.
2. Clear Area: Clear work area of people, pets, and obstacles. Watch for hidden objects like wires or rocks.
3. Fuel Safety: Mix fuel outdoors. Use only STIHL 2-stroke oil and 89 octane minimum gasoline. Store fuel in approved container.
4. Operation: Hold unit firmly with both hands. Keep cutting attachment below waist level. Do not operate on unstable surfaces.
5. Hot Surfaces: Avoid contact with muffler and cylinder during/after operation.

WARNING! This trimmer produces toxic exhaust fumes. Operate only in well-ventilated areas. Never operate indoors.

Assembly & Preparation

Unpack all parts. Assembly requires attaching the handle, cutting attachment, and debris shield.

1. Attach Loop Handle: Slide onto shaft at marked position, align, and tighten clamping screws securely.
2. Install Debris Shield: Slide onto shaft from front, align with mounting points, and secure with provided screws.
3. Attach Cutting Head: Ensure drive shaft is clean. Thread PolyCut head onto drive shaft clockwise until hand-tight. Use appropriate tool to secure firmly (do not overtighten).
4. Install Line: Follow instructions on head packaging to wind new line onto spool. Feed ends through eyelets.
5. Check Controls: Ensure throttle trigger moves freely and lockout functions. Check stop switch operation.

CAUTION! Ensure all fasteners are tight before operation. Loose parts can become dangerous projectiles.

Specifications

• Model: STIHL FS 45 C
• Engine Type: Single cylinder, 2-stroke, air-cooled
• Displacement: 27.2 cc (1.66 cu. in.)
• Power Output: 0.9 kW (1.2 bhp)
• Idle Speed: 2,800 rpm
• Max. Engine Speed: 12,500 rpm
• Fuel/Oil Ratio: 50:1 (STIHL 2-stroke oil)
• Fuel Tank Capacity: 0.4 liters (13.5 fl oz)
• Cutting Swath: Approx. 16 inches (40 cm)
• Sound Pressure Level: Approx. 96 dB(A)
• Vibration Levels (left/right): 4.5/5.5 m/s²
• Weight (without cutting attachment): 4.6 kg (10.1 lbs)

Controls and Components

Familiarize yourself with all controls before starting.

Main Components: Throttle trigger, throttle trigger lockout, stop switch, choke lever, purge bulb (primer), fuel tank cap, handle, shaft, debris shield, cutting head.

Operation: To operate, press and hold the throttle trigger lockout, then squeeze the throttle trigger. Release the lockout to idle or stop. The stop switch moves to the STOP position to kill the engine.

Choke/Start Settings: Lever has three positions: RUN (normal operation), START/CHOKE (cold start), and WARM START/HALF-CHOKE (warm engine restart).

Fuel & Lubrication

Use only fresh, unleaded gasoline with a minimum octane rating of 89 and STIHL 2-stroke engine oil.

1. Fuel Mixing: Mix at a 50:1 ratio. Use a clean, approved fuel container. Add oil first, then gasoline. Close container and shake thoroughly.
2. Filling Fuel: Place unit on a level surface. Clean area around cap. Unscrew cap slowly. Fill tank to about 1 cm below rim. Tighten cap securely.
3. Gearbox Lubrication: The gearbox at the cutting head is filled with grease at the factory. Check periodically for leaks or excessive wear.

WARNING! Gasoline is extremely flammable. No smoking. Mix and fill outdoors, away from sparks or flames. Wipe up spills immediately.

Starting & Stopping

Starting (Cold Engine):

1. Place unit on firm, flat ground. Ensure cutting head is clear.
2. Press purge bulb (primer) 5-10 times until fuel is visible.
3. Move choke lever to START/CHOKE position.
4. Press throttle trigger lockout and squeeze throttle trigger once, then release both.
5. Grasp handle firmly, place foot in loop handle. Pull starter rope briskly until engine fires (usually 1-3 pulls).
6. Immediately move choke lever to WARM START/HALF-CHOKE position.
7. Pull starter rope again until engine starts and runs.
8. Allow engine to warm up at idle for 30 seconds. Choke lever will move automatically to RUN.

Starting (Warm Engine): Follow steps 1, 4, 5, and 7 with choke lever in RUN or WARM START position.

Stopping: Release throttle trigger. Allow engine to idle briefly. Move stop switch to STOP position.

Operating Instructions

Hold unit with right hand on rear handle (throttle) and left hand on loop handle.

1. Swing Technique: Use a smooth, swinging motion from right to left, keeping the cutting head parallel to the ground and slightly angled.
2. Cutting Height: Cut only the top 1/3 of grass/weeds for healthy growth. Avoid scalping.
3. Line Advance (Tap'N'Go™): With engine at high speed, gently tap the cutting head on the ground. Do not bang aggressively.
4. Trimming Near Objects: Use the tip of the line for precision. Keep the shield between you and the cutting head.
5. Taking Breaks: Stop engine during transport or when not actively cutting.

CAUTION! Never operate with a damaged shield or cutting attachment. Do not use metal blades or other non-approved attachments.

Maintenance & Cleaning

Perform maintenance only when engine is off and cool. Disconnect spark plug boot for safety.

1. Air Filter: Clean weekly under dusty conditions. Remove cover, take out foam filter, wash in warm soapy water, dry, and re-oil lightly with STIHL filter oil.
2. Spark Plug: Check gap (0.020" / 0.5 mm) and clean electrode periodically. Replace if worn.
3. Spark Arrestor Screen (Muffler): Clean monthly. Remove muffler cover and screen, carbon with a wire brush.
4. Cutting Head: Remove tangled debris. Replace worn line spool. Check for cracks.
5. Exterior: Wipe unit clean with a damp cloth. Keep cooling fins and air intakes clear.

WARNING! Use only STIHL replacement parts. Improper parts can cause unsafe operation and void warranty.

Storage

For storage longer than 30 days:

1. Drain fuel tank completely and run carburetor dry.
2. Remove spark plug, add a teaspoon of engine oil into cylinder, pull starter rope slowly to distribute, reinstall plug.
3. Clean entire unit thoroughly.
4. Store in a dry, locked place, out of reach of children.
5. Protect cutting head from deformation (do not hang unit by the head).

CAUTION! Storing with fuel in the tank can cause gum deposits in the carburetor. Use fuel stabilizer if you must store with fuel.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel; flooded; spark plug faulty; switch in STOP; clogged air filter	Check fuel; wait if flooded; check/replace spark plug; ensure switch is RUN; clean air filter.
Engine starts but dies	Dirty fuel filter; clogged fuel tank vent; carburetor adjustment	Replace fuel filter; clean tank vent; have dealer adjust carburetor.
Loss of power	Clogged air filter; dirty spark arrestor; old fuel	Clean air filter and spark arrestor screen; use fresh fuel mix.
Excessive vibration	Damaged cutting attachment; loose fasteners; bent shaft	Inspect and replace damaged head; tighten all screws; inspect shaft.
Line does not advance	Line tangled; spool empty; head mechanism dirty	Remove tangle; reload line; clean head or replace spool.
Cutting head rotates at idle	Idle speed too high	Have dealer adjust idle speed (carburetor adjustment).

Service: For repairs beyond basic maintenance, contact an authorized STIHL servicing dealer.

Warranty: Refer to the separate warranty statement. Keep your dated proof of purchase.