Stihl MS361 Repair Manual

The Stihl MS361 is a professional-grade chainsaw known for its power, reliability, and advanced engine technology. This repair manual provides comprehensive guidance for maintenance, troubleshooting, and repair procedures for the MS361 model. Below are key sections covering safety, specifications, disassembly, engine repair, fuel system, ignition system, bar and chain, troubleshooting, and reassembly.

Safety Precautions

Before performing any repair, ensure the chainsaw is turned off and the spark plug is disconnected. Wear appropriate personal protective equipment (PPE).

Hazard	Precaution
Fuel handling	Work in well-ventilated area; no open flames
Sharp components	Wear cut-resistant gloves when handling chain
Hot surfaces	Allow engine to cool completely before disassembly
Electrical shock	Disconnect spark plug wire
Chemical exposure	Use gloves when handling fuel/oil mixtures

Specifications & Technical Data

• Engine Type: 2-stroke, single cylinder
• Displacement: 59.0 cm³ (3.6 cu. in.)
• Power Output: 3.4 kW (4.6 hp)
• Fuel/Oil Ratio: 50:1 (Stihl HP Ultra or equivalent)
• Ignition System: Electronic, capacitor discharge
• Carburetor: Walbro or Zama diaphragm type
• Bar Length Range: 40 cm (16") to 50 cm (20")
• Chain Pitch: 3/8" or .325"
• Weight (powerhead): 5.9 kg (13.0 lbs)

Tools Required

Standard and Stihl-specific tools needed for repair.

1. Torx screwdrivers (T27, T20)
2. Spark plug wrench (13/16")
3. Compression tester
4. Carburetor adjustment tool
5. Piston stop tool
6. Flywheel puller (Stihl 1129)
7. Clutch removal tool
8. Torque wrench (calibrated in Nm)

NOTE: Use genuine Stihl tools or equivalents to avoid damage.

Disassembly Procedure

Step-by-step guide to safely disassemble the MS361.

1. Remove bar and chain: Loosen side cover nuts, remove cover, then bar and chain.
2. Remove top cover: Remove screws securing top cover/handle assembly.
3. Remove fuel tank: Drain fuel; disconnect fuel lines; remove tank screws.
4. Remove carburetor: Disconnect throttle linkage and fuel lines; remove mounting screws.
5. Remove cylinder cover: Remove screws; carefully lift off cover.
6. Remove muffler: Remove mounting nuts; detach muffler from cylinder.

WARNING! Label all parts and fasteners; take photos during disassembly for reference.

Engine Repair

Procedures for piston, cylinder, crankshaft, and bearings.

Cylinder & Piston Inspection: Check for scoring, carbon buildup, ring wear. Measure piston clearance (spec: 0.045-0.055 mm).

Crankshaft & Bearings: Check for play; replace if axial play exceeds 0.3 mm. Use puller for bearing removal.

Seals: Replace crankcase seals if leaking (use sealant Stihl 0881).

Torque Specifications: Cylinder bolts: 10 Nm; Connecting rod bolts: 10 Nm; Clutch: 40 Nm.

Fuel System

Fuel tank, lines, filter, and pump repair.

1. Drain fuel completely.
2. Replace fuel filter and lines (cracked lines cause air leaks).
3. Inspect fuel tank for cracks; clean vent.
4. Test fuel pump (if equipped): Apply pressure check.

Tip: Use Stihl fuel line (part #0000 350 3200) for replacement.

Ignition System

Spark plug, coil, flywheel, and switch testing.

Component	Test Procedure	Specification
Spark Plug	Check gap (0.5 mm); replace if fouled	NGK BPMR7A or equivalent
Ignition Coil	Resistance test: primary 0.2-0.3 Ω, secondary 8-10 kΩ	Replace if out of spec
Flywheel	Check magnets; key alignment	No cracks; key intact
Stop Switch	Continuity test when pressed	Open circuit when off

Bar & Chain Maintenance

Guide bar maintenance, chain sharpening, and sprocket inspection.

1. Clean bar groove: Remove debris with bar groove cleaner.
2. Check bar wear: Even wear on both sides; replace if uneven or grooved.
3. Sharpen chain: Use round file (size per chain pitch); maintain 30° angle.
4. Inspect drive sprocket: Replace if worn (tip: replace sprocket with every second chain).
5. Lubrication: Ensure oiler passage is clear; adjust oil flow as needed.

CAUTION! Always wear gloves when handling chain.

Carburetor Adjustment

Adjusting H, L, and LA screws on Walbro or Zama carburetor.

1. Initial settings: Turn H and L screws gently clockwise to seat, then back out H 1 turn, L 1 turn.
2. Start engine; warm up for 5 minutes.
3. Adjust L screw: Turn for smoothest idle without chain movement.
4. Adjust H screw: For maximum RPM (do not exceed 13,500 rpm no-load).
5. Adjust LA (idle speed): Set so chain does not move at idle.

WARNING! Over-leaning H screw can cause engine damage.

Reassembly Guide

Reverse of disassembly with critical notes.

1. Install crankshaft seals with sealant.
2. Apply piston ring compressor when installing cylinder.
3. Torque bolts to specification (see Engine Repair section).
4. Prime carburetor with fuel before starting.
5. Check for fuel and air leaks before full operation.

NOTE: Perform compression test after reassembly (minimum 120 psi).

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, fuel issue, flooded	Check spark, fuel lines, dry plug
Engine runs then dies	Fuel filter clogged, vent blocked	Replace filter, clear tank vent
Loss of power	Clogged air filter, exhaust screen	Clean/replace filter, remove screen carbon
Chain won't turn	Clutch worn, sprocket damaged	Inspect clutch springs, replace sprocket
Excessive vibration	Muffler loose, crank imbalance	Tighten muffler, check crankshaft bearings
Oil not dispensing	Oiler clogged, pump faulty	Clean oil passages, replace oil pump

Service Support: For genuine parts and technical assistance, contact Stihl authorized service or visit www.stihlusa.com.