Stihl FS 72 Manual

The Stihl FS 72 is a professional-grade string trimmer/brushcutter designed for demanding clearing and trimming tasks. It features a powerful 2-stroke engine with electronic ignition, a robust gearbox, a straight shaft, and a versatile cutting head system for use with trimmer line or metal blades. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 2-stroke engine, Anti-Vibration System (AVS), Ergonomic handle, QuickStop® inertia chain brake, Decompression valve, Straight drive shaft, and a versatile attachment interface.

Feature	Description
Engine Type	2-stroke, single-cylinder, air-cooled
Displacement	Specific to FS 72 model (e.g., 31.8 cc)
Ignition System	Electronic, capacitor discharge (CDI)
Fuel System	Diaphragm carburetor
Drive Shaft	Straight, solid steel
Gearbox	Heavy-duty, grease-lubricated
Anti-Vibration	AVS system in handle and shaft
Starter	Rewind starter with decompression valve
Cutting Attachments	Accepts trimmer heads, circular blades, brush knives
Handle	Loop handle with controls

Safety Information

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

1. Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, sturdy gloves, long pants, and boots.
2. Work Area Safety: Clear area of bystanders, especially children and pets. Be aware of hidden objects like wires or rocks.
3. Fuel Safety: Refuel in a well-ventilated area with engine off and cool. Use only STIHL-approved fuel mix.
4. Operation Safety: Hold unit firmly with both hands. Maintain secure footing. Do not operate above shoulder height.
5. Kickback Zone: Be aware of the danger zone at the tip of the cutting attachment.

WARNING! Failure to follow safety instructions can result in serious injury or death. The cutting tool can throw objects at high speed.

Assembly & First Use

Unpack all parts. Assembly typically requires attaching the handle, cutting attachment, and harness.

1. Handle Attachment: Position loop handle on shaft at comfortable operating height. Tighten clamping screws securely.
2. Cutting Attachment: Ensure engine is off. Fit chosen trimmer head or blade onto drive shaft, secure with retaining nut using appropriate tool.
3. Harness: Attach STIHL harness according to instructions to reduce operator fatigue.
4. Fuel Mix: Prepare fuel: Use high-quality 2-stroke engine oil mixed with unleaded gasoline at the ratio specified in the manual (e.g., 50:1). Shake well.
5. Starting: Place unit on clear, flat ground. Engage chain brake. Set master control lever to cold start position. Pull starter cord briskly.

CAUTION! Ensure all fasteners are tight before operation. Never use a cutting attachment that is damaged or incorrect for the machine.

Specifications

• Model: STIHL FS 72
• Engine Power: Specific kW/HP rating for FS 72.
• Displacement: e.g., 31.8 cm³
• Fuel/Oil Ratio: 50:1 (STIHL 2-Stroke Oil) or as specified.
• Idle Speed: Factory set (e.g., 2800 rpm).
• Maximum Powerhead RPM: Specific to model.
• Sound Pressure Level: Meets relevant directives (e.g., LpA).
• Vibration Levels: Front/Rear handle values per test standards.
• Weight (powerhead): Approx. weight in kg/lbs.
• Shaft Type: Straight solid shaft.
• Warranty: STIHL limited warranty period.

Controls and Components

Master Control Lever: Combines stop switch, choke, and run positions. Throttle Trigger: Located on rear handle, controls engine speed. Throttle Trigger Lockout: Must be depressed to allow throttle operation. Chain Brake Lever (if equipped): Stops cutting attachment in event of kickback. Decompression Valve: Reduces pulling force for starting. Primer Bulb: For easier cold starting.

Main Components: Fuel Tank, Air Filter Cover, Spark Plug, Muffler, Starter Grip, Drive Shaft Housing, Gearbox, Cutting Attachment Retaining Nut.

Fuel & Lubrication

Use only clean, fresh unleaded gasoline (min. 89 octane) mixed with a high-quality 2-stroke engine oil designed for air-cooled engines.

1. Fuel Mix: Always use the exact ratio specified (e.g., 50:1). Use STIHL 2-Stroke Oil or equivalent meeting ISO-L-EGD standards.
2. Mixing: Mix in a clean, approved fuel can. Add oil to gasoline and shake vigorously.
3. Gearbox Lubrication: Lubricate gearbox with STIHL special gear grease periodically or as specified in maintenance.
4. Storage: For long-term storage, run engine dry or use fuel stabilizer.

WARNING! Gasoline is highly flammable. No smoking. Avoid sparks. Wipe up spills immediately.

Operation Guide

1. Starting (Cold): Set master control to choke (⏻). Press primer bulb 5-10 times. Engage chain brake. Pull starter cord until engine 'fires'. Move master control to half-throttle position. Pull starter cord again to start. Blip throttle to disengage choke.
2. Starting (Warm): Master control in run position. Pull starter cord.
3. Running: Allow engine to warm up at idle for ~30 seconds. Release chain brake before applying throttle.
4. Cutting Technique: Use a smooth, sweeping motion from right to left (for right-hand operators). Let the tip of the line/blade do the work. Avoid pushing into material.
5. Stopping: Release throttle, allow engine to idle briefly. Move master control lever to STOP (0).

Tip: Maintain a firm grip and stable stance. Take frequent breaks.

Cutting Attachments

Acceptable attachments: STIHL PolyCut head (trimmer line), circular grass blades, brush knives, and metal saw blades.

1. Trimmer Line (PolyCut): For grass and weeds. Advance line by tapping head on ground at high RPM ("Tap-n-Go").
2. Grass Blades: 2-tooth or 4-tooth for thick grass and light brush.
3. Brush Knives: 3-tooth or more for heavy brush and saplings.
4. Metal Saw Blades: For cutting small trees and woody material.
5. Changing Attachments: Use STIHL combination wrench or socket to hold shaft and loosen/tighten retaining nut. Follow specific instructions for each head type.

WARNING! Always use the correct guard for the attachment. Ensure cutting tool is sharp, balanced, and undamaged.

Maintenance Schedule

Interval	Task
Daily / Before Use	Check for loose fasteners, damage. Clean exterior. Check cutting attachment.
Every 10 hrs / Weekly	Clean air filter. Check spark plug condition.
Every 20 hrs	Clean spark arrestor screen in muffler (if equipped).
Every 50 hrs	Lubricate gearbox with special grease. Check fuel filter.
Every 100 hrs / Annually	Replace fuel filter. Check carburetor adjustment (by trained technician).
As Needed	Replace trimmer line. Sharpen or replace blades.

CAUTION! Disconnect spark plug boot before performing any maintenance except refueling.

Storage

For storage longer than 30 days, prepare the engine to prevent fuel system damage.

1. Run the engine until it stops to use up fuel in the carburetor.
2. Drain any remaining fuel from the tank into an approved container.
3. Remove spark plug, add a teaspoon of engine oil into the cylinder, pull starter cord slowly 2-3 times to coat internals, reinstall plug.
4. Thoroughly clean the entire unit.
5. Store in a dry, secure place, out of reach of children.

Tip: Using a fuel stabilizer in the last tank before storage is an alternative to draining.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No fuel; flooded; bad spark; master control position	Check fuel. Move control to run/warm start. Check spark plug. Wait if flooded.
Engine starts then dies	Clogged fuel filter; dirty air filter; carburetor issues	Replace fuel filter. Clean air filter. May need carb service.
Loss of power	Dirty air filter; clogged spark arrestor; old fuel	Clean/replace air filter. Clean spark arrestor screen. Use fresh fuel mix.
Excessive vibration	Damaged cutting attachment; loose parts; bent shaft	Inspect blade/head for damage or imbalance. Tighten all fasteners.
Cutting attachment does not spin	Sheared drive shaft pin; clutch issues; gearbox failure	Check shear pin. Inspect clutch springs. Consult authorized STIHL dealer.
Trimmer line won't advance	Empty spool; tangled line; worn head	Refill spool. Rewind line neatly. Replace head if worn.

Service: For repairs beyond basic maintenance, contact an authorized STIHL servicing dealer. Use only genuine STIHL parts.

Support: STIHL Incorporated, www.stihlusa.com. Refer to your local dealer for specific warranty and service inquiries.