stihl ms 250 service manual free download

The STIHL MS 250 is a professional-grade, lightweight chainsaw designed for demanding cutting tasks. This service manual provides comprehensive information for maintenance, troubleshooting, and repair. It covers the engine, fuel system, ignition, clutch, chain brake, guide bar, and cutting chain. Below are key sections for safety, specifications, maintenance procedures, troubleshooting, and parts identification.

Features at a Glance

Key components: STIHL 2-MIX engine, Quickstop® inertia-activated chain brake, side-access chain tensioner, Ematic™ lubrication system, and anti-vibration system.

Feature	Description
Engine Type	STIHL 2-MIX single-cylinder, two-stroke
Displacement	45.4 cc (2.77 cu. in.)
Power Output	2.6 kW (3.5 bhp)
Fuel Tank Capacity	0.47 L (16 oz.)
Oil Tank Capacity	0.26 L (8.8 oz.)
Guide Bar Lengths	16" (40 cm) or 18" (45 cm)
Chain Pitch	3/8" PMM
Weight (powerhead)	5.2 kg (11.5 lbs)
Ignition System	Electronic, capacitor discharge (CDI)
Starter	STIHL ErgoStart™ (optional)

Safety Information

Always wear protective equipment: helmet, eye protection, hearing protection, gloves, chainsaw chaps, and sturdy boots.

1. Pre-Operation Check: Inspect chainsaw for damage, ensure chain brake functions, check chain tension and sharpness.
2. Fueling: Use clean, approved fuel mix (50:1 gasoline to STIHL HP Ultra oil). Refuel in well-ventilated area, away from ignition sources.
3. Operation: Maintain secure footing, keep bystanders away, be aware of kickback zone.
4. Transport: Engage chain brake, fit scabbard over guide bar.

WARNING! Failure to follow safety instructions can result in serious injury or death. Read and understand the operator's manual before use.

Technical Specifications

• Engine: 45.4 cc single-cylinder two-stroke with STIHL 2-MIX technology.
• Powerhead Weight: 5.2 kg (11.5 lbs).
• Fuel/Oil Mix: 50:1 (Gasoline to STIHL HP Ultra 2-stroke oil).
• Idle Speed: 2,800 rpm.
• Maximum Power Speed: 13,000 rpm.
• Ignition Air Gap: 0.30 mm (0.012 in).
• Spark Plug: Bosch WSR 6 F or equivalent, gap 0.5 mm (0.020 in).
• Carburetor: Zama C1Q-S199 or equivalent.
• Chain Oil: STIHL HP Ultra or equivalent biodegradable chain oil.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity. Follow this schedule based on usage hours.

Daily/Before Use: Check chain tension and sharpness, inspect guide bar, check all nuts/bolts, clean air filter, check fuel/oil levels.

Weekly/Every 10 Hours: Clean spark arrestor screen (if equipped), inspect spark plug, clean cooling fins, check clutch drum and sprocket.

Monthly/Every 50 Hours: Replace spark plug, clean fuel filter, check fuel lines, inspect anti-vibration elements, check chain brake function.

Annually/Every 100 Hours: Clean carburetor, check cylinder/piston through exhaust port, replace air filter, inspect clutch springs.

Engine Service

Cylinder and Piston: Remove muffler to inspect piston and cylinder for scoring. Crankshaft Seals: Check for leaks using pressure/vacuum test. Decompression Valve: Clean and ensure it seals properly.

1. Remove top cover, air filter, and carburetor to access engine.
2. Use a piston stop to hold crankshaft when removing clutch or flywheel.
3. Torque flywheel nut to 40 Nm (30 ft-lb) and clutch to 40 Nm (30 ft-lb).

Tip: Always use genuine STIHL parts or equivalents for service.

Fuel System

Components: Fuel tank, filter, lines, carburetor (Zama C1Q-S199).

1. Fuel Filter: Replace if clogged. Access through filler neck with filter hook.
2. Fuel Lines: Inspect for cracks/hardness. Replace if damaged.
3. Carburetor Adjustment: Standard settings: L=1 turn out, H=1 turn out. Fine-tune for optimal performance.
4. Fuel Pump Diaphragm: Check for flexibility; replace if stiff or cracked.

WARNING! Use only clean, fresh fuel mix. Old fuel can cause starting and performance issues.

Ignition System

Electronic CDI module, spark plug, stop switch, flywheel.

1. Spark Test: Remove spark plug, connect to ignition wire, ground against cylinder, pull starter. Look for strong blue spark.
2. Air Gap: Set between flywheel and ignition module legs to 0.30 mm (0.012 in).
3. Stop Switch Test: Disconnect wire from module; if engine starts, switch is faulty.
4. Module Resistance: Check with multimeter per manual specifications.

CAUTION! Never pull starter with spark plug disconnected and not grounded.

Chain & Guide Bar

Maintain sharp chain and clean guide bar groove.

Chain Sharpening: Use correct round file size (4.0 mm / 5/32" for 3/8" PMM chain). Maintain 30° cutting angle, 10° top plate filing angle. Depth gauges should be filed to 0.65 mm (0.025 in) below cutter.

Guide Bar: Clean groove with bar groove cleaner. Rotate bar regularly for even wear. Check for straightness and wear at sprocket nose.

Chain Tension: Correct when snug against bar but can be pulled around by hand. Adjust with side-access tensioner when chain is cool.

Clutch & Sprocket

Centrifugal clutch with drum sprocket.

1. Clutch Removal: Use clutch tool (STIHL 0000 893 4300) to hold drum; turn clockwise to remove.
2. Inspection: Check clutch shoes for wear, springs for damage or stretch.
3. Sprocket: Replace if worn (teardrop-shaped drive links). Use rim sprocket system for easier replacement.
4. Bearing: Check clutch drum bearing for smooth rotation; replace if rough.

Tip: Engage chain brake before servicing clutch area.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, fuel issue	Check spark, dry plug, clean air filter, check fuel lines/filter.
Engine starts then dies	Fuel filter clogged, carburetor adjustment	Replace fuel filter, adjust L screw, check fuel tank vent.
Loss of power	Clogged spark arrestor, dirty air filter	Clean spark arrestor screen, replace air filter.
Chain does not stop immediately (brake failure)	Brake band worn, mechanism dirty	Replace brake band, clean linkage and springs.
Excessive vibration	Loose parts, unbalanced chain, worn AV mounts	Tighten all fasteners, sharpen chain evenly, replace AV buffers.
Chain oil not flowing	Oil hole clogged, pump defective	Clean oil passages, check oil pump drive and diaphragm.

Reset: For electronic issues, disconnect spark plug wire and pull starter 5-6 times to clear flood.

Service: For technical support or genuine parts, contact an authorized STIHL dealer.

Parts Diagrams

Refer to the official STIHL MS 250 parts catalog for exploded views and part numbers. Common replacement parts include:

• Air Filter: Part # 0000 120 1620
• Spark Plug: Bosch WSR 6 F / Part # 0000 400 1300
• Fuel Filter: Part # 0000 350 3501
• Complete Carburetor Kit: Part # 0000 120 0650
• Clutch Assembly: Part # 0000 160 4011
• Chain Brake Band: Part # 0000 350 3100
• Guide Bar, 16": Part # 3003 000 2016
• Oregon 72DL 3/8" PMM Chain: Part # 63PM 72

Disclaimer: This manual is for reference only. Always consult an authorized STIHL service dealer for complex repairs.