Stihl 090 Manual

The Stihl 090 is a professional-grade chainsaw known for its high power output and durability, designed for heavy-duty logging and milling applications. It features a large displacement engine, robust construction, anti-vibration system, and advanced safety features. Below are key sections for safety, features, operation, maintenance, troubleshooting, and specifications.

Features at a Glance

Key components: High-torque two-stroke engine, Anti-Vibration System (AVS), Decompression valve, Chain brake, Quick-stop inertia brake, Adjustable oil pump, Large fuel and oil tanks.

Feature	Description
Engine Displacement	High cc for maximum power output
Anti-Vibration System (AVS)	Reduces operator fatigue during extended use
Decompression Valve	Easier starting by reducing cylinder pressure
Chain Brake	Stops chain immediately in kickback situations
Quick-stop Inertia Brake	Additional safety brake activated by inertia
Adjustable Oil Pump	Controls chain lubrication rate
Fuel Tank Capacity	Large volume for extended operation
Oil Tank Capacity	Ample chain oil supply
Bar Length Options	Compatible with long guide bars for milling
Throttle Interlock	Prevents accidental throttle activation

Safety Instructions

Read all instructions before operation. Always wear appropriate PPE.

1. Personal Protective Equipment: Wear safety glasses, hearing protection, gloves, chainsaw chaps, and steel-toe boots.
2. Work Area Safety: Clear area of obstacles and ensure secure footing.
3. Kickback Prevention: Hold saw firmly with both hands; be aware of kickback zone.
4. Fuel Safety: Refuel in well-ventilated area away from ignition sources.

WARNING! Never operate chainsaw with damaged or missing safety features. Keep bystanders at a safe distance.

Assembly & Preparation

Unpack and inspect all components. Assemble guide bar and chain.

1. Attach Guide Bar: Place bar onto mounting studs, align chain tensioning pin.
2. Install Chain: Ensure cutting teeth face forward on top of bar.
3. Tension Chain: Adjust tension screw until chain snaps back when pulled from bar.
4. Fill Tanks: Add recommended fuel mix to fuel tank and bar/chain oil to oil tank.

CAUTION! Ensure chain is properly tensioned and moves freely before starting.

Specifications

• Engine Type: Two-stroke, single cylinder.
• Displacement: High cc (specific to 090 model).
• Power Output: High horsepower for heavy-duty cutting.
• Fuel System: Diaphragm carburetor with manual choke.
• Ignition System: Electronic ignition (CDI).
• Bar Length Range: Up to 36 inches or more.
• Chain Pitch/Gauge: .404" pitch, .063" gauge (typical).
• Weight: Heavy-duty construction weight.
• Fuel/Oil Ratio: 50:1 with STIHL HP Ultra oil or equivalent.
• Sound Power Level: High dB(A) - hearing protection required.

Controls and Components

Main controls located on rear handle and body. Front Handle: Chain brake lever, throttle lockout. Rear Handle: Throttle trigger, master control lever, decompression valve button.

Master Control Lever: Combines choke, start, and run positions. Throttle Trigger: Controls engine speed. Chain Brake Lever: Manual activation forward of front handle. Decompression Valve: Button to reduce cylinder pressure for easier starting. Chain Tensioner: Screw adjustment on side cover.

Starting & Operation

Cold Start Procedure: Engage chain brake. Set master control to choke. Press decompression valve. Pull starter rope until engine fires. Move control to half-throttle position. Pull again to start. Warm Start: Master control in run position only.

1. Secure footing and grip saw firmly with both hands.
2. Disengage chain brake by pulling back toward operator.
3. Apply slight throttle to bring to operating speed.
4. Begin cut with lower quadrant of bar tip to avoid kickback.
5. Let chain do the work - avoid forcing the saw.

Tip: Always idle saw for brief period before shutting down to stabilize engine temperature.

Maintenance Schedule

Daily: Clean air filter, check chain tension, inspect chain sharpness. Weekly: Clean cooling fins, check spark plug, inspect bar for wear. Monthly: Clean fuel filter, check anti-vibration elements, inspect clutch and sprocket.

1. Air Filter: Remove and clean with compressed air or soapy water (dry completely).
2. Spark Plug: Check gap (0.020"), clean electrodes, replace if worn.
3. Chain Brake: Test function regularly - should stop chain within milliseconds.
4. Bar Maintenance: Clean bar groove, flip bar regularly for even wear.

WARNING! Perform maintenance only when saw is completely cool and spark plug wire disconnected.

Chain Sharpening & Tensioning

Proper chain maintenance is critical for performance and safety.

1. Sharpening: Use round file matching chain pitch. Maintain 30° cutting angle and 10° top plate angle.
2. Depth Gauges: File down to proper height (0.025" below cutter) using depth gauge tool.
3. Tensioning: Loosen bar nuts, adjust tension screw until chain snaps back when pulled from bar.
4. Retighten: Secure bar nuts after tensioning, recheck tension after brief use.

CAUTION! Always wear gloves when handling chain. Keep file strokes even for consistent sharpening.

Fuel & Lubrication

Use fresh fuel mixture. Never use straight gasoline or automotive oil.

Fuel Mix: 50:1 ratio with 89+ octane gasoline and STIHL HP Ultra 2-cycle oil. Chain Oil: Use STIHL chain oil or equivalent for bar lubrication. Storage: For long-term storage, run carburetor dry or use fuel stabilizer.

Storage Guidelines

Clean saw thoroughly before storage. Empty fuel tank or add stabilizer. Remove chain and store in oil. Store in dry, secure location away from children.

CAUTION! Fuel left in carburetor can cause starting problems. Run engine dry or use fuel stabilizer.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel issues, spark plug, flooding	Check fuel mixture, clean spark plug, use decompression valve, avoid over-choking.
Engine runs poorly	Clogged air filter, carburetor adjustment	Clean/replace air filter, adjust high and low speed screws per manual.
Chain doesn't turn	Clutch issues, drive sprocket	Check clutch springs and shoes, inspect sprocket for wear.
Excessive vibration	AV mounts, loose components	Inspect anti-vibration mounts, tighten all fasteners.
Chain oil not flowing	Clogged oil passages, pump failure	Clean oil ports, check pump operation, use proper oil viscosity.

Service: For major repairs, contact authorized STIHL service dealer.

Support: STIHL customer service or visit www.stihlusa.com