stihl 028 av service manual pdf

The STIHL 028 AV is a professional-grade chainsaw known for its Anti-Vibration (AV) system, robust construction, and reliable performance. This service manual provides comprehensive information for maintenance, troubleshooting, and repair of the STIHL 028 AV chainsaw. It covers safety procedures, technical specifications, engine components, fuel system, ignition system, cutting equipment, and detailed step-by-step repair instructions. Below are key sections for safety, features, maintenance, troubleshooting, and parts information.

Features and Specifications

Key components: Engine, Anti-Vibration system, Chain Brake, Decompression Valve, OILOMATIC chain lubrication.

Feature	Description
Engine Type	Single cylinder, two-stroke, air-cooled
Displacement	Approx. 51.5 cc (3.14 cu. in.)
Power Output	Approx. 3.0 kW (4.0 hp)
Fuel Tank Capacity	Approx. 0.55 liters (18.6 fl. oz.)
Oil Tank Capacity	Approx. 0.26 liters (8.8 fl. oz.)
Guide Bar Lengths	Typically 16" to 20" (40 cm to 50 cm)
Chain Pitch	3/8" PM or .325"
Ignition System	Electronic, breakerless
Anti-Vibration System	Spring-mounted handles and engine isolation
Weight (without cutting equipment)	Approx. 5.9 kg (13.0 lbs)

Safety Information

Always wear appropriate Personal Protective Equipment (PPE) including safety glasses, hearing protection, gloves, chainsaw chaps, and sturdy boots.

1. Before starting work: Ensure the chainsaw is on a stable surface, chain brake is engaged, and the chain is clear of obstructions.
2. During operation: Maintain a firm grip with both hands, keep bystanders at a safe distance, and be aware of kickback zones.
3. After use: Engage the chain brake, allow the saw to cool, and store fuel/oil separately in approved containers.
4. Transport: Secure the saw with the chain guard installed.

WARNING! Never operate a chainsaw that is damaged or improperly maintained. Always use genuine STIHL parts and follow all local safety regulations.

Maintenance Schedule

Regular maintenance is crucial for safety, performance, and longevity.

1. Daily/Before Each Use: Check chain tension and sharpness, inspect guide bar for wear, check all fasteners for tightness, clean air filter, check fuel and oil levels.
2. Weekly/After 5 Hours: Clean spark plug, check spark arrestor screen (if equipped), inspect fuel filter, check anti-vibration elements.
3. Monthly/After 20 Hours: Clean cooling fins, check carburetor adjustment, inspect clutch and sprocket, clean exhaust port and muffler.
4. Annually/After 100 Hours: Replace fuel filter, replace spark plug, check piston and cylinder through exhaust port, inspect all rubber mounts and AV buffers.

CAUTION! Use only STIHL-approved lubricants and fuel mixtures (typically 50:1 gasoline to 2-stroke oil).

Engine Components

• Cylinder and Piston: Inspect for scoring, carbon buildup, and ring wear. Measure piston clearance.
• Crankshaft and Bearings: Check for play and smooth rotation. Replace if excessive wear is detected.
• Carburetor (Typical: Bing or Zama): Adjust idle (L) and high-speed (H) screws. Clean jets and diaphragm. Use a pressure/vacuum tester for leaks.
• Rewind Starter: Inspect spring, pawls, and rope. Lubricate as needed.
• Decompression Valve: Ensure it opens and closes freely to aid starting.
• Muffler: Remove and clean carbon deposits. Check for cracks.

Fuel System

Includes fuel tank, cap, lines, filter, and carburetor.

Fuel Mixture: Use fresh, unleaded gasoline (min. 89 octane) mixed with a high-quality 2-stroke engine oil at a 50:1 ratio (for oils labeled for 50:1). For older oils, a 40:1 ratio may be specified. Check your oil container.

Fuel Filter: Located inside the tank. Replace if clogged or annually.

Fuel Lines: Check for cracks, brittleness, or leaks. Replace if damaged.

Carburetor Adjustment (Basic): With engine warm, adjust idle speed screw (LA) so chain does not move and engine runs smoothly. Adjust low-speed (L) and high-speed (H) screws for optimal performance. Refer to specific carburetor manual for detailed settings.

Ignition System

Electronic ignition module, spark plug, and stop switch.

1. Spark Plug: Use recommended type (e.g., Bosch WSR6F, NGK BPMR7A). Gap: 0.5 mm (0.020"). Clean electrode and check for cracks.
2. Ignition Module: Test with an ignition tester. Check for spark when pulling starter with plug grounded to cylinder. No spark indicates a faulty module, broken wire, or faulty stop switch.
3. Air Gap: Between flywheel and ignition module coil legs is critical (approx. 0.3 mm / 0.012"). Adjust if necessary.
4. Stop Switch: Test for continuity. Should be open circuit when in "RUN" position.

Tip: Always disconnect the spark plug boot before performing any maintenance.

Cutting Equipment

Includes guide bar, saw chain, drive sprocket, clutch, and chain brake.

1. Guide Bar: Inspect for straightness, groove wear, and burrs on rails. Dress rails with a flat file. Lubricate sprocket nose.
2. Saw Chain: Sharpen regularly with correct round file size. Maintain proper depth gauge setting. Check for damaged or loose rivets.
3. Drive Sprocket: Inspect for wear (especially rim sprockets). Replace if teeth are hooked or worn.
4. Clutch: Check springs and shoes for wear. Clean centrifugal clutch of wood chips and oil.
5. Chain Brake: Test functionality. Inspect band for cracks and mechanism for free movement. Clean and lubricate pivot points.
6. Chain Tension: Adjust so chain snaps back lightly when pulled from underside of bar. Re-tighten after initial use.

WARNING! Always use a matched set of guide bar, chain, and sprocket with the correct pitch and gauge.

Anti-Vibration System

The AV system uses rubber buffers and springs to isolate the engine/handle assembly from the cutting equipment.

Inspection: Check all rubber AV mounts (front and rear) for cracking, hardening, or disintegration. Check spring washers and bolts for tightness.

Replacement: Worn AV elements can cause excessive vibration, leading to user fatigue and potential damage. Replace as a set for balanced performance.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, fuel issue, compression	Check spark, plug condition. Dry plug if flooded. Check fuel mix, filter, lines. Check compression (should be >100 psi).
Engine starts but dies	Clogged fuel filter, carburetor adjustment, air leak	Replace fuel filter. Adjust carburetor L/H screws. Check for air leaks at crank seals, intake manifold.
Lacks power under load	Clogged air filter, muffler screen, carburetor, fuel vent	Clean/replace air filter. Clean spark arrestor screen. Adjust carburetor H screw. Check tank vent.
Chain does not stop when brake is engaged	Worn brake band, dirty mechanism	Inspect brake band for wear. Clean and lubricate brake mechanism.
Excessive vibration	Worn AV mounts, unbalanced chain, bent bar	Replace AV buffers. Sharpen chain evenly. Check guide bar for straightness.
Chain oil not flowing	Empty oil tank, clogged oil passages, faulty pump	Fill tank. Clean bar groove and oil holes. Check oil pump drive and adjust output.

Reset: For electronic issues, disconnect spark plug to reset ignition module.

Parts List and Diagrams

Refer to the official STIHL 028 AV Illustrated Parts List for exploded views and part numbers. Common replacement parts include:

• Cylinder & Piston Kit
• Carburetor Repair Kit
• Ignition Module
• Starter Assembly
• AV Buffer Set
• Clutch Assembly
• Oil Pump
• Guide Bar and Chain Set

CAUTION! Always use genuine STIHL replacement parts to ensure compatibility, safety, and performance.

Warranty and Support

STIHL products are backed by a limited warranty. Proof of purchase from an authorized STIHL dealer is required. This manual is for reference only. For complex repairs, it is recommended to seek service from an authorized STIHL servicing dealer.

Support: For technical assistance, parts, or to locate a dealer, visit the official STIHL website at www.stihlusa.com or contact STIHL customer service.

Copyright © STIHL. STIHL and OILOMATIC are registered trademarks of ANDREAS STIHL AG & Co. KG. All rights reserved.