Stihl MS390 Chainsaw Manual

The Stihl MS390 is a professional-grade chainsaw featuring a powerful engine, robust construction, and advanced safety features. Designed for demanding cutting tasks, it includes an anti-vibration system, QuickStop® inertia chain brake, STIHL Ematic™ lubrication system, and a decompression valve for easier starting. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Engine, Guide Bar, Saw Chain, Chain Brake Lever, Throttle Trigger, Master Control Lever, Fuel Tank, Oil Tank, and Muffler.

Assembly & Preparation

Unpack and inspect all parts. Assemble on a clean, stable surface.

1. Attach Guide Bar and Chain: Place bar on studs, tensioning pin in hole. Fit chain over sprocket and bar, ensuring cutting teeth face forward on top.
2. Adjust Chain Tension: Loosen nuts, turn tensioning screw until chain fits snugly against bar (lift slightly at center). Retighten nuts.
3. Fill Fuel Tank: Use fresh fuel mix (50:1 gasoline to STIHL HP Ultra oil). Do not use automotive oil or old gasoline.
4. Fill Oil Tank: Use STIHL chain oil or equivalent for bar lubrication.

WARNING! Always wear protective gear (gloves, eye/ear protection, chainsaw chaps, helmet). Ensure chain brake is functional before starting.

First-Time Operation

Perform pre-start checks and start the engine safely.

1. Check Chain Tension: Chain should lift slightly from bar but not hang loose.
2. Check Chain Brake: Pull brake lever forward until it clicks (engaged). Push back to disengage.
3. Start Engine: Place on ground, engage chain brake. Set Master Control to cold start (choke). Pull starter rope until engine fires, then move lever to run position. Pull again to start.
4. Warm Up: Allow engine to idle for 30 seconds before cutting.

CAUTION! Never start the saw in mid-air or without proper footing. Keep bystanders at least 15 feet away.

Specifications

• Engine Displacement: 64.1 cc (3.91 cu in).
• Power Output: 3.6 kW (4.8 hp).
• Fuel/Oil Ratio: 50:1 (STIHL HP Ultra).
• Guide Bar Lengths: 16" to 20" (40 cm to 50 cm).
• Chain Pitch/Gauge: 3/8" P / .050" (1.3 mm).
• Weight (powerhead): Approx. 13.2 lbs (6.0 kg).
• Sound Pressure Level: 106 dB(A).
• Vibration Levels: Front/Rear handle: 4.5/2.5 m/s².
• Ignition System: Electronic, capacitor discharge.
• Warranty: Limited warranty for personal/professional use.

Controls and Functions

Master Control Lever: Combines stop switch (0), run position (I), and choke/fast idle (⏚). Throttle Trigger: Controls engine speed; includes throttle lockout. Chain Brake Lever: Manual engagement; inertia-activated. Decompression Valve: Reduces compression for easier starting. Fuel/Oil Caps: Marked for easy identification.

Starting Procedure: Engage chain brake. Set Master Control to choke. Pull starter until engine fires. Move lever to run. Pull again to start. Disengage brake before cutting.

Chain & Bar Setup

Proper chain installation ensures safe and efficient cutting.

1. Ensure saw is off and cool.
2. Loosen bar nuts with combination wrench.
3. Turn tensioning screw to adjust chain. Correct tension: chain snaps back when pulled from bar.
4. Tighten bar nuts securely while lifting tip of bar.
5. Check lubrication: Run saw briefly and inspect for oil on chain.

Tip: Always check chain tension before each use and after initial warm-up.

Safe Operation Procedures

Supports felling, limbing, bucking, and pruning.

1. Personal Protective Equipment: Wear helmet, face shield, ear protection, gloves, chainsaw chaps, and steel-toe boots.
2. Pre-Cut Inspection: Check chain sharpness, tension, lubrication, and brake function.
3. Cutting Technique: Use full throttle when cutting; let chain do the work. Avoid kickback zone (upper tip of bar).
4. Refueling: Stop engine and allow to cool. Wipe area clean. Use fuel can with spout.
5. Transport: Engage chain brake; fit scabbard over bar.

WARNING! Never operate above shoulder height or with one hand. Be aware of kickback forces.

Maintenance Schedule

Daily: Clean air filter, check chain tension/sharpness, inspect bar for wear. Weekly: Clean cooling fins, check spark plug, clean fuel filter. Monthly: Clean spark arrestor screen, check all fasteners, replace fuel filter if needed. Annually: Professional servicing recommended.

Care & Storage

Clean saw after each use. Remove chain and bar; clean grooves and oil holes. Store in dry place, away from ignition sources. For long-term storage: Drain fuel tank, run engine dry, remove chain and store separately.

CAUTION! Do not use pressure washers or solvents. Keep handles clean and dry.

Regulatory Information

EPA & CARB compliant for emissions. Meets ANSI B175.1 safety standards. Copyright © STIHL Incorporated. All rights reserved. For genuine parts and accessories, visit authorized STIHL dealers. For support, contact STIHL USA at 1-800-467-8445 or www.stihlusa.com.

Troubleshooting

Reset: For electronic issues, disconnect spark plug wire for 30 seconds.

Service: 1-800-467-8445; www.stihlusa.com. Use only STIHL-approved parts.