MS250 Chainsaw Manual

The MS250 is a professional-grade gasoline chainsaw designed for demanding cutting tasks. It features a powerful 2-stroke engine, anti-vibration system, quick-stop chain brake, automatic chain oiling, and easy-start technology. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 2-stroke engine, guide bar, cutting chain, anti-vibration handles, chain brake, throttle trigger, choke control, fuel tank, oil tank.

Feature	Description
Engine displacement	45.4 cc professional-grade engine
Power output	2.6 kW (3.5 hp) for high cutting performance
Guide bar length	16-inch standard (options: 14", 18")
Chain pitch/gauge	.325" pitch, .063" gauge
Weight (powerhead)	5.2 kg (11.5 lbs) without bar and chain
Fuel tank capacity	470 ml (0.5 US qt)
Oil tank capacity	260 ml (0.27 US qt)
Anti-vibration system	Reduces operator fatigue during extended use
Chain brake	Quick-stop inertia-activated safety feature
Automatic chain oiling	Ensures proper lubrication during operation

Assembly & Preparation

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

1. Attach guide bar: Loosen bar nuts, position bar on studs, align chain sprocket.
2. Install cutting chain: Place chain over bar with cutting teeth facing forward, engage drive links in bar groove.
3. Tension chain: Adjust tensioning screw until chain snaps back when pulled from bar.
4. Secure bar nuts: Tighten evenly to specified torque (9-11 Nm).
5. Fill fuel tank: Use fresh gasoline/oil mixture (50:1 ratio).
6. Fill oil tank: Use high-quality bar and chain oil.

WARNING! Always wear protective gear: helmet, goggles, gloves, ear protection, and chainsaw chaps.

First-Time Operation

Perform pre-start checks before initial use.

1. Check chain tension: Chain should be snug against bar but pull freely.
2. Test chain brake: Pull hand guard forward; chain should stop immediately.
3. Set master control lever: Push to choke position (cold start) or run position (warm start).
4. Prime fuel system: Press primer bulb 5-10 times until fuel is visible.
5. Start engine: Place on ground, hold front handle with left hand, pull starter rope briskly.
6. Warm up: Allow engine to run at idle for 30 seconds before cutting.

CAUTION! Never start chainsaw while holding it in the air. Always maintain secure footing.

Specifications

• Engine Type: 2-stroke, single cylinder, air-cooled.
• Displacement: 45.4 cc.
• Power Output: 2.6 kW (3.5 hp) at 9,000 rpm.
• Maximum Engine Speed: 13,500 rpm.
• Idle Speed: 2,800 rpm.
• Fuel/Oil Ratio: 50:1 (high-quality 2-stroke oil).
• Spark Plug: Bosch WSR6F or equivalent.
• Sound Pressure Level: 106 dB(A) at operator's ear.
• Vibration Levels: Front handle: 4.2 m/s², Rear handle: 6.5 m/s².
• Warranty: 2 years commercial use, 4 years private use.

Controls and Functions

Master Control Lever: Combines choke, throttle lock, and stop functions. Throttle Trigger: Controls engine speed. Throttle Lockout: Prevents accidental throttle engagement. Chain Brake Lever: Manual activation. Hand Guard: Inertia-activated chain brake. Decompression Valve: Reduces pulling force for starting.

Starting Procedure: 1. Engage chain brake. 2. Set master control to choke. 3. Press decompression valve. 4. Pull starter rope until engine fires. 5. Move control to run position. 6. Pull starter rope to start.

Stopping: Move master control to stop position or press stop switch.

Chain & Bar Maintenance

Proper maintenance ensures optimal performance and safety.

1. Daily chain sharpening: Use round file (4.0 mm) at 30° angle, maintain consistent depth gauges.
2. Weekly bar maintenance: Clean bar grooves, flip bar monthly for even wear.
3. Chain tension check: Adjust when chain sags more than 2mm from bar.
4. Sprocket inspection: Replace if teeth show significant wear.
5. Oil flow verification: Run chainsaw over cardboard; oil line should appear within 30 seconds.

Tip: Always stop engine and allow chain to cool before maintenance.

Fuel & Oil Mixing

Use fresh unleaded gasoline (minimum 89 octane) mixed with high-quality 2-stroke oil.

1. Mixing ratio: 50:1 (20 ml oil per 1 liter gasoline).
2. Mixing procedure: Add oil to approved fuel container, then add gasoline.
3. Shake thoroughly: Mix for 30 seconds before filling tank.
4. Storage: Use fuel within 30 days; add fuel stabilizer for longer storage.
5. Bar oil: Use all-season chainsaw oil; switch to winter-grade below 32°F (0°C).

WARNING! Never use automotive oil, diesel fuel, or ethanol blends above 10%. Never mix fuel near open flame.

Safety Features

Chain Brake: Stops chain within milliseconds if kickback occurs. Throttle Lockout: Prevents accidental throttle engagement. Right-Hand Guard: Protects from chain breakage. Anti-Vibration System: Reduces fatigue and improves control. Chain Catcher: Prevents broken chain from striking operator. Spark Arrestor: Reduces fire risk in dry conditions.

Storage & Cleaning

Prepare chainsaw for storage if not used for more than 30 days.

1. Drain fuel tank: Run engine until it stops from fuel starvation.
2. Clean air filter: Remove, wash in soapy water, dry completely.
3. Remove chain and bar: Clean thoroughly, coat with oil.
4. Clean cooling fins: Remove debris from cylinder fins.
5. Store properly: In dry location, away from children, with chain brake engaged.

CAUTION! Never store with fuel in tank for extended periods. Fuel deteriorates and can damage engine components.

Regulatory Information

EPA Certified: Meets EPA Phase 2 emissions standards. CARB Compliant: Approved for use in California. EU Emission Standards: Meets Stage II requirements. Noise Emission: Complies with ANSI B175.1 standards. Contains FCC Part 15 Class B digital device components. Copyright © 2023. For support, visit www.stihl.com or contact 1-800-GO-STIHL.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Old fuel, clogged filter, flooded engine	Use fresh fuel mix, clean air filter, wait 10 minutes if flooded.
Engine starts then dies	Fuel line blockage, carburetor issues	Clean fuel filter, check fuel lines, adjust carburetor.
Chain doesn't turn	Brake engaged, clutch worn, sprocket issues	Disengage chain brake, inspect clutch springs, check drive sprocket.
Excessive vibration	Loose components, unbalanced chain	Tighten all fasteners, sharpen chain evenly, balance bar.
Chain throws oil	Over-oiling, wrong oil viscosity	Adjust oil flow rate, use correct bar oil for temperature.
Poor cutting performance	Dull chain, improper filing	Sharpen chain correctly, maintain proper depth gauge height.

Service Intervals: Air filter: Every 10 hours. Spark plug: Every 50 hours. Fuel filter: Every 100 hours. Carburetor adjustment: Annually or as needed.

Authorized Service: 1-800-GO-STIHL; www.stihl.com