stihl ms 250 repair manual pdf

The STIHL MS 250 is a professional-grade chainsaw designed for demanding cutting tasks. This repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair of the MS 250 model. It covers engine systems, fuel system, ignition, chain drive, lubrication, and electrical components. Below are key sections for safety, specifications, maintenance procedures, troubleshooting, and parts identification.

1. Safety Precautions 2. Technical Specifications 3. Maintenance Schedule 4. Engine Repair 5. Fuel System 6. Ignition System 7. Chain & Bar Assembly 8. Lubrication System 9. Electrical System 10. Troubleshooting Guide 11. Parts Diagram

Safety Precautions

Always prioritize safety when performing repairs on the STIHL MS 250 chainsaw.

Safety Item	Description
Personal Protective Equipment	Wear safety glasses, gloves, hearing protection, and chainsaw chaps
Work Area	Work in a well-ventilated area away from sparks or open flames
Fuel Safety	Drain fuel tank before repairs; no smoking near fuel
Chain Safety	Remove spark plug wire and ensure chain brake is engaged
Tool Safety	Use proper tools; follow torque specifications
Electrical Safety	Disconnect spark plug before working on ignition system
Sharp Edges	Handle cutting edges with care; wear cut-resistant gloves
Lifting	Lift with legs, not back; chainsaw weighs approximately 10.1 lbs
Cleanliness	Keep work area clean to prevent slips and falls
Manual Reference	Always consult manual before attempting repairs

Technical Specifications

Key technical data for the STIHL MS 250 chainsaw.

Engine Type: 2-stroke, single cylinder, air-cooled
Displacement: 45.4 cc (2.77 cu. in.)
Power Output: 2.6 kW (3.5 bhp)
Fuel Capacity: 0.53 US pt (0.25 l)
Oil Capacity: 0.35 US pt (0.17 l)
Idle Speed: 2,800 rpm
Maximum Power Speed: 13,000 rpm
Chain Pitch: 3/8" PMM3 or 0.325"
Bar Length Range: 16" to 20"
Weight (without cutting equipment): 10.1 lbs (4.6 kg)

WARNING! Always use STIHL-approved parts and lubricants. Using non-approved components may void warranty and cause damage.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

Daily: Check chain tension, sharpness, and lubrication
After each use: Clean air filter, check for loose fasteners
Weekly: Inspect spark plug, fuel filter, and bar condition
Monthly: Clean cooling fins, check anti-vibration elements
Every 3 months: Replace spark plug, clean carburetor
Every 6 months: Replace fuel filter, check fuel lines
Annually: Check compression, replace air filter
As needed: Sharpen chain, replace worn sprocket

CAUTION! Perform maintenance only when engine is cool and spark plug disconnected.

Engine Repair

Cylinder & Piston: Inspect for scoring; replace if wear exceeds 0.004"
Crankcase: Check for cracks; seal with STIHL sealant
Crankshaft: Inspect bearings; replace if play exceeds 0.002"
Carburetor: Adjust H and L screws; factory setting: H=1, L=1
Muffler: Clean spark arrestor screen regularly
Compression Test: Should read 120-150 psi
Decompression Valve: Test for proper sealing
Rebuild Kit: STIHL part number 0000 400 1300

Fuel System

Fuel system components and repair procedures.

Fuel Tank: Capacity 0.53 US pt. Fuel Lines: Replace if cracked or hardened. Fuel Filter: Replace every 6 months. Carburetor: Zama C1Q-S267. Fuel Mix: 50:1 with STIHL HP Ultra oil. Primer Bulb: Test for cracks; replace if leaking. Fuel Cap: Ensure vent is clear. Leak Test: Pressurize system to 7 psi; hold for 30 seconds.

Ignition System

Ignition troubleshooting and component replacement.

Disconnect spark plug wire before servicing
Spark Plug: NGK BPMR7A, gap 0.020"
Ignition Module: STIHL part 4140 400 1301
Spark Test: Should jump 1/4" gap
Kill Switch: Test continuity; replace if faulty
Flywheel: Check keyway; torque to 44 ft-lbs
Coil Air Gap: 0.010" (0.25 mm)

Tip: Use dielectric grease on spark plug boot to prevent moisture intrusion.

Chain & Bar Assembly

Chain drive system maintenance and repair.

Chain Tension: Adjust so chain snaps back when pulled
Bar Rails: File smooth if burred; replace if worn unevenly
Sprocket: Replace if wear marks exceed 0.5 mm
Clutch: Inspect shoes for wear; replace if worn 50%
Chain Brake: Test function; replace band if stretched
Guide Bar: Rotate regularly for even wear
Oil Holes: Ensure bar oil holes are clear
Drive Sprocket: Torque to 44 ft-lbs

WARNING! Always stop engine and engage chain brake before adjusting chain.

Lubrication System

Automatic oiler system maintenance.

Electrical System

STIHL MS 250 features electronic ignition and stop switch.

Component	Test Procedure	Specification
Ignition Coil	Primary resistance	0.5-1.5 ohms
Kill Switch	Continuity test	Closed when pressed
Wiring Harness	Visual inspection	No cracks or breaks
Spark Plug Cap	Resistance test	5,000 ohms ± 20%

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, fuel issue, flooded	Check spark, clean carburetor, dry plug
Engine runs poorly	Dirty air filter, bad fuel	Replace filter, use fresh fuel mix
Chain won't turn	Clutch worn, sprocket damaged	Inspect clutch, replace sprocket
Excessive vibration	Loose fasteners, unbalanced parts	Tighten all fasteners, check crankshaft
Oil leakage	Cracked oil tank, bad seals	Replace oil tank, install new seals
Overheating	Dirty cooling fins, lean mixture	Clean fins, adjust carburetor
No chain oil	Clogged oiler, empty tank	Clean oil passages, fill tank
Hard starting when hot	Ignition coil failing	Test coil resistance when hot

Reset: After repairs, reset carburetor to factory settings.

Service: For technical support: 1-800-467-8445; www.stihlusa.com

Parts Diagram

Refer to STIHL parts catalog for MS 250. Key part numbers:

Cylinder: 1128 020 1205
Piston: 1128 030 2001
Carburetor: 1128 120 0650
Ignition Module: 4140 400 1301
Clutch: 1128 160 2001
Chain Brake Band: 1128 792 4800
Fuel Line: 1118 358 7700
Air Filter: 1128 140 0600

Note: Always use genuine STIHL parts for optimal performance and safety.