Stihl 051 AV Manual

The Stihl 051 AV is a professional-grade chainsaw featuring Anti-Vibration (AV) technology, designed for demanding forestry and cutting applications. This manual covers essential information for safe operation, maintenance, troubleshooting, and specifications to ensure optimal performance and longevity of your chainsaw.

Safety Instructions

Always wear appropriate personal protective equipment (PPE): helmet, eye protection, hearing protection, gloves, chainsaw chaps, and steel-toed boots.

Hazard	Precaution
Kickback	Hold saw firmly with both hands; keep chain sharp and properly tensioned; avoid contact with tip.
Fuel Handling	Refuel in well-ventilated area with engine off and cool; use approved fuel containers.
Electrical Hazards	Do not operate near power lines or electrical sources.
Exhaust Fumes	Operate only in well-ventilated outdoor areas.
Falling Debris	Be aware of overhead branches and falling material.

WARNING! Never operate a chainsaw when fatigued, under the influence, or in adverse weather conditions.

Features & Components

Key components: Anti-Vibration system, electronic ignition, decompression valve, adjustable automatic oiler, side-access chain tensioner, and safety throttle lock.

Component	Description
Engine	2-stroke, single-cylinder, air-cooled
Displacement	77.5 cc
Power Output	5.5 hp
Guide Bar Length	20-28 inches (standard)
Chain Pitch	3/8" or .404" (depending on configuration)
Weight (powerhead)	Approx. 15.4 lbs (7.0 kg)
Fuel Tank Capacity	26.4 fl oz (780 ml)
Oil Tank Capacity	11.9 fl oz (350 ml)

Assembly & Preparation

Unpack and inspect all components. Assemble on a clean, flat surface.

1. Attach guide bar and chain: Place bar on studs, align chain with sprocket, adjust tension using side-access knob.
2. Fill fuel tank: Mix high-quality 2-stroke oil with unleaded gasoline (50:1 ratio for standard Stihl oil).
3. Fill chain oil tank: Use Stihl chain oil or equivalent for proper lubrication.
4. Check controls: Ensure throttle trigger, throttle lock, and stop switch function correctly.

CAUTION! Always check chain brake function before each use.

Technical Specifications

• Model: Stihl 051 AV
• Engine Type: 2-stroke single cylinder
• Displacement: 77.5 cm³
• Power Output: 4.1 kW (5.5 hp)
• Maximum Engine Speed: 9,500 rpm
• Idle Speed: 2,800 rpm
• Fuel/Oil Ratio: 50:1 (with Stihl 2-stroke oil)
• Ignition System: Electronic, capacitor discharge
• Starting System: Rewind starter
• Chain Oiling: Automatic with manual override
• Sound Pressure Level: 112 dB(A)
• Vibration Levels: Front handle: 4.5 m/s²; Rear handle: 5.5 m/s²

Controls & Operation

Master control lever: Combines stop switch, choke, and fast idle. Throttle lockout: Must be depressed before throttle can be engaged. Chain brake: Manual/automatic activation via front hand guard.

Starting Procedure:

1. Engage chain brake.
2. Set master control to cold start position (choke).
3. Press decompression valve (if equipped).
4. Place saw on ground, hold firmly with foot in rear handle.
5. Pull starter rope briskly until engine fires.
6. Move master control to half-throttle position.
7. Pull starter rope until engine starts.
8. Briefly blip throttle to disengage fast idle.

Stopping: Release throttle, allow engine to idle, push stop switch to "0".

Fuel & Lubrication

Use fresh unleaded gasoline with minimum 89 octane. Mix with high-quality 2-stroke engine oil specifically for air-cooled engines.

1. Fuel mixture: 50:1 ratio (2% oil) when using Stihl 2-stroke oil.
2. Chain oil: Use proper bar and chain oil for all temperatures.
3. Never use straight gasoline, automotive motor oil, or recycled oil.
4. Clean fuel cap area before opening to prevent contamination.

Tip: Use fuel stabilizer if storing for more than 30 days.

Maintenance Schedule

Regular maintenance ensures safety and performance.

Interval	Task
Daily/Before use	Check chain tension, sharpness, and lubrication; inspect for loose fasteners; test chain brake
Every 10 hours	Clean air filter; check spark plug; clean cooling fins
Every 20 hours	Clean spark arrestor screen; check fuel filter
Every 50 hours	Replace fuel filter; clean carburetor air passage
Every 100 hours	Check cylinder/piston through exhaust port; replace spark plug
Annually	Professional inspection of all safety systems

Chain & Bar Care

Proper chain maintenance is critical for safety and cutting performance.

1. Sharpening: Use correct round file size (typically 7/32" for 3/8" chain). Maintain 30° cutting angle.
2. Tensioning: Chain should snap back when pulled from bar with light force.
3. Rotation: Regularly rotate bar to ensure even wear.
4. Groove cleaning: Clean bar groove and oil holes weekly.
5. Depth gauges: File depth gauges to maintain proper height (0.025" below cutter).

WARNING! Always wear cut-resistant gloves when handling chain.

Storage Guidelines

Prepare chainsaw for storage to prevent fuel system damage and corrosion.

1. Drain fuel tank and run engine until it stops to clear carburetor.
2. Remove chain, clean thoroughly, and soak in oil.
3. Clean entire saw, especially cooling fins and air filter.
4. Store in dry, secure location away from children.
5. For long-term storage, fog engine with preservative oil.

CAUTION! Never store with fuel in tank for more than 30 days.

Warranty Information

Stihl 051 AV comes with a limited warranty covering defects in materials and workmanship. Warranty period varies by region (typically 1 year for consumer use, 90 days for commercial use). Keep purchase receipt for warranty validation. Warranty does not cover normal wear, improper maintenance, or use of non-Stihl parts. For warranty claims, contact authorized Stihl servicing dealers only.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, flooded, fuel issues	Check spark plug; use correct starting procedure; ensure fresh fuel mix.
Engine runs poorly	Clogged air/fuel filter, carb adjustment	Clean/replace filters; adjust carburetor (H/L screws).
Chain doesn't oil	Clogged oil passages, empty tank	Clean oil ports; fill tank; check oil pump function.
Chain won't stop	Worn clutch, brake malfunction	Inspect clutch springs; test brake band and mechanism.
Excessive vibration	Loose components, damaged AV mounts	Tighten all fasteners; inspect anti-vibration elements.
Overheating	Dirty cooling fins, lean mixture	Clean fins; check carburetor settings; use proper fuel mix.

Service: For complex repairs, contact authorized Stihl dealer. Use only genuine Stihl replacement parts.