STIHL Trimmer Maintenance Manual

The STIHL Trimmer Maintenance Manual provides comprehensive guidance for the safe and effective upkeep of your STIHL string trimmer or brushcutter. Proper maintenance is essential for optimal performance, longevity, and operator safety. This manual covers routine checks, cleaning procedures, fuel system care, cutting attachment maintenance, and troubleshooting common issues. Always refer to your specific model's operator manual for detailed specifications.

1. Safety Precautions 2. Daily Maintenance Checklist 3. Fuel System & Engine Care 4. Cutting Attachment Maintenance 5. Air Filter & Cooling System 6. Spark Plug & Ignition System 7. Drive Shaft & Gearbox 8. Storage Procedures 9. Troubleshooting Guide 10. Parts & Specifications

Safety Precautions

Before performing any maintenance, ensure the trimmer is turned off, the spark plug wire is disconnected, and all moving parts have come to a complete stop. Wear appropriate personal protective equipment (PPE) including gloves and safety glasses.

Precaution	Description
Disconnect Spark Plug	Prevents accidental engine start-up during maintenance.
Cool Engine	Allow engine to cool before handling or refueling.
Secure Unit	Place trimmer on a stable, flat surface.
Use Genuine Parts	Only use STIHL-approved replacement parts and accessories.
Proper Fuel Handling	Use clean, fresh fuel mix; avoid spills and store fuel properly.

Daily Maintenance Checklist

Perform these checks before and after each use to ensure safe operation.

Visual Inspection: Check for loose screws, cracks, or damage on the housing, shaft, and cutting attachment.
Cutting Tool: Inspect trimmer line or blade for wear, damage, or dullness. Replace as needed.
Debris Clearance: Clean grass, dirt, and debris from the engine cooling fins, air filter cover, and cutting guard.
Fuel Check: Ensure proper fuel mixture (e.g., 50:1 gasoline to 2-cycle oil) is used and tank is free of contaminants.
Start Test: Verify smooth starting and idle operation; listen for unusual noises.

WARNING! Never operate a trimmer that shows signs of damage or malfunction. Repair before use.

Fuel System & Engine Care

Proper fuel and engine maintenance is critical for performance and preventing carburetor issues.

Fuel Mixture: Always use fresh, high-octane gasoline mixed with STIHL 2-cycle engine oil at the specified ratio (typically 50:1).
Fuel Filter: Replace the in-tank fuel filter annually or if clogged.
Carburetor Adjustment: Use a tachometer to set idle and high-speed screws per manufacturer specs if engine runs poorly.
Fuel Tank: Clean tank periodically and inspect for cracks or leaks.
Decarbonization: Remove and clean the muffler spark arrestor screen regularly to prevent carbon buildup.

CAUTION! Fuel is highly flammable. Work in a well-ventilated area away from ignition sources.

Cutting Attachment Maintenance

Trimmer Line: Replace monofilament line when worn below minimum length. Wind new line onto spool following directional arrows.
Metal Blades: Sharpen dull blades with a file or grinding wheel, maintaining the original cutting angle. Balance the blade after sharpening.
Guard & Shield: Inspect for cracks and secure attachment. Clean debris after each use.
Drive Shaft Connection: Ensure cutting attachment is securely fastened to the drive shaft. Lubricate splines with STIHL grease if specified.
Bump Feed System: For auto-feed heads, tap on ground to advance line; ensure spool rotates freely.

Air Filter & Cooling System

A clean air filter ensures proper air-fuel mixture and protects the engine from abrasive particles.

Cleaning Procedure: Remove air filter cover and filter element. Tap filter on a hard surface to dislodge loose dirt or wash in warm, soapy water if foam type. Allow to dry completely before re-oiling (if applicable) and reinstalling.

Cooling Fins: Use a brush or compressed air to remove grass clippings and dirt from the cylinder cooling fins. Overheating can cause severe engine damage.

Inspection Interval: Clean air filter every 10 operating hours or more frequently in dusty conditions. Replace if damaged.

Spark Plug & Ignition System

Inspect spark plug periodically for fouling, wear, or incorrect gap.

Disconnect spark plug wire and remove plug with appropriate socket wrench.
Check electrode for erosion and ceramic insulator for cracks or carbon tracking.
Clean electrodes with a wire brush. Set gap to specification (typically 0.020 inches / 0.5 mm) using a feeler gauge.
Reinstall plug hand-tight, then tighten an additional 1/4 to 1/2 turn. Reconnect wire securely.
Replace spark plug annually or after every 100 operating hours.

Tip: A properly gapped, clean spark plug ensures reliable starting and efficient combustion.

Drive Shaft & Gearbox

Lubrication of the drive shaft and gearhead is essential for smooth operation and longevity.

Drive Shaft Lubrication: For models with a removable shaft, apply STIHL special shaft grease periodically as per manual.
Gearbox Care: Check gearbox for leaks and unusual noise. Lubricate with STIHL gear grease annually or every 50 hours.
Flexible Drive Shaft: Ensure it is not kinked or damaged. Replace if signs of wear appear.
Bearing Inspection: Rotate shaft by hand to check for smooth rotation; gritty feeling indicates worn bearings.

WARNING! Do not attempt to disassemble sealed gearboxes. Service by an authorized STIHL dealer if needed.

Storage Procedures

Proper storage prevents fuel system problems and corrosion.

Short-Term (Under 30 days): Drain fuel tank or add fuel stabilizer. Run engine for 2 minutes to circulate treated fuel through carburetor. Store in a clean, dry place.

Long-Term (Over 30 days): Completely drain fuel tank and carburetor. Run engine until it stops to use up all fuel. Remove spark plug, add a teaspoon of 2-cycle oil into cylinder, pull starter cord slowly to coat interior, reinstall plug. Clean entire unit and store with cutting attachment removed.

CAUTION! Never store trimmer with fuel in the tank for extended periods without stabilizer. Old fuel can gum up carburetor.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	Old fuel, clogged filter, faulty spark plug	Use fresh fuel mix, clean/replace filter, check/replace spark plug.
Engine runs poorly or dies	Dirty air filter, clogged fuel filter, carburetor issue	Clean air filter, replace fuel filter, have carburetor serviced.
Excessive vibration	Unbalanced blade, bent shaft, loose parts	Balance or replace blade, inspect shaft, tighten all fasteners.
Line not advancing	Worn spool, tangled line, dirty head	Replace spool, rewind line correctly, clean cutting head.
Loss of power	Clogged muffler, carbon buildup, worn piston/cylinder	Clean spark arrestor screen, decarbonize, inspect for engine wear.

Dealer Service: For complex repairs (e.g., carburetor rebuild, engine overhaul), contact an authorized STIHL servicing dealer.

Parts & Specifications

Engine Type: 2-stroke, air-cooled.
Fuel/Oil Ratio: Typically 50:1 (Gasoline : STIHL 2-Cycle Oil).
Spark Plug: BOSCH or NGK equivalent, gap 0.020" (0.5 mm).
Air Filter: Polyurethane foam or felt element.
Cutting Attachments: Monofilament line heads, metal blades (circular, tri-blade).
Drive System: Flexible shaft or rigid shaft with gearhead.
Lubricants: STIHL Super Clean 2-Stroke Oil, STIHL HP Ultra 2-Stroke Oil, STIHL Special Shaft Grease.
Warranty: Refer to your STIHL warranty card for terms and period.

Support: For genuine parts, accessories, and service, visit www.stihlusa.com or locate your local STIHL dealer.