Stihl MS361 Service Manual

The Stihl MS361 is a professional-grade chainsaw featuring a 59.0 cc engine, electronic ignition (CDI), anti-vibration system, QuickStop® inertia chain brake, STIHL EMM (Electronic Motor Management) for optimized performance, side-access chain tensioner, tool-less fuel and oil caps, and a decompression valve. This manual provides essential information for maintenance, troubleshooting, repair, and safe operation procedures. Below are key sections covering safety, specifications, maintenance schedules, component servicing, and troubleshooting.

Features at a Glance

Key components: Engine cylinder, Carburetor (Zama C1Q-S199 or equivalent), Air filter system, Chain brake assembly, Decompression valve, Muffler, Fuel and oil tanks.

Feature	Description
Engine Displacement	59.0 cc (3.6 cu. in.)
Power Output	3.6 kW (4.9 hp)
Fuel Tank Volume	0.55 L (18.6 fl. oz.)
Oil Tank Volume	0.26 L (8.8 fl. oz.)
Guide Bar Lengths	40 cm (16"), 45 cm (18"), 50 cm (20")
Chain Pitch	3/8" or .325"
Ignition System	Electronic CDI
Weight (powerhead)	5.9 kg (13.0 lbs)
Anti-Vibration	Standard
Chain Brake	QuickStop® inertia activated

Safety Information

Always wear appropriate PPE: safety glasses, hearing protection, gloves, chainsaw chaps, and sturdy boots.

1. Before servicing: Ensure engine is off, spark plug wire disconnected, and unit cooled down.
2. Fuel handling: Use fresh fuel mix (50:1 STIHL HP Ultra or equivalent). No smoking.
3. Chain tension: Check and adjust when cold; proper tension reduces kickback risk.
4. Chain brake: Test function before each use.

WARNING! Never operate a chainsaw without proper training. Keep bystanders away. Avoid contact with moving chain.

Technical Specifications

• Engine Type: Single cylinder, 2-stroke, air-cooled.
• Bore x Stroke: 46 mm x 35.2 mm.
• Idle Speed: 2,800 RPM (adjustable).
• Maximum Power Speed: 9,500 RPM.
• Spark Plug: NGK BPMR 7A (gap 0.5 mm / 0.020").
• Fuel/Oil Ratio: 50:1 with STIHL HP Ultra oil.
• Carburetor: Zama C1Q-S199 (standard adjustments: LA=1 turn, H=1 turn).
• Chain Oil: STIHL chain oil or equivalent.
• Sound Pressure Level: 106 dB(A).
• Vibration Level: Front handle 4.2 m/s², rear handle 3.8 m/s².

Maintenance Schedule

Access components via removal of covers and fasteners. Use STIHL special tools where specified.

Daily/Before Use: Check chain tension, sharpness, and lubrication; inspect air filter; verify chain brake function.

Every 10 Hours: Clean air filter; check spark plug; clean cooling fins; inspect fuel filter.

Every 20 Hours: Clean spark arrestor screen; check carburetor settings; inspect anti-vibration elements.

Every 50 Hours: Replace fuel filter; clean carburetor; check cylinder/piston through exhaust port.

Annually/100 Hours: Replace spark plug; inspect clutch, sprocket, and bar rails; full carburetor service if needed.

Component Identification & Controls

Front Handle: Throttle trigger, throttle lockout, choke/start lever. Rear Handle: Master control lever (combines choke, stop, run). Side Panel: Chain brake handle, decompression valve, side-access chain tensioner.

Controls: Master Control Lever (choke, stop, run), Throttle Trigger Lockout, Chain Brake Handle, Decompression Valve, Fuel/Oil Caps, Chain Tensioner.

Maintenance Points: Air filter cover, Spark plug access, Muffler cover, Clutch cover, Chain catcher, Anti-vibration springs.

Fuel System & Carburetor

Fuel Tank: Remove tank cover to access fuel filter and line. Carburetor: Located under air filter housing.

1. Fuel filter replacement: Use hook tool to extract filter from tank.
2. Carburetor adjustment: Initial settings LA=1 turn open, H=1 turn open. Fine-tune at operating temperature.
3. Diaphragm inspection: Check for cracks or stiffness; replace kit if necessary.
4. Fuel line: Inspect for cracks; replace if leaking or brittle.

Tip: Always use fresh fuel mix to prevent carburetor varnish and clogging.

Ignition System

CDI module, spark plug, stop switch, wiring harness.

1. Spark plug: Remove, clean, check gap (0.5 mm), replace if electrodes worn.
2. Ignition coil air gap: Set to 0.3 mm (0.012") using feeler gauge.
3. Stop switch test: Use multimeter to check continuity when pressed.
4. CDI testing: Check for spark with plug grounded; if none, replace CDI.

WARNING! Disconnect spark plug wire before servicing ignition components.

Chain & Bar Maintenance

Supports .325" or 3/8" pitch chains. Bar lengths 16"-20".

1. Chain sharpening: Use round file matching chain pitch (typically 4.0 mm for .325"). Maintain 30° top plate angle.
2. Bar maintenance: Clean groove, flip regularly, file rails if burred.
3. Drive sprocket: Inspect for wear; replace if teeth hooked.
4. Chain tension: Adjust when cold; proper tension = snug against bar but pullable by hand.
5. Oil flow check: Run at idle over light surface; should see oil line.

WARNING! Always wear gloves when handling chain. Ensure chain brake is engaged during maintenance.

Cooling & Exhaust System

Air cooling fins, muffler with spark arrestor screen.

Cleaning cooling fins: Remove covers, use brush to clear debris. Muffler: Remove to clean carbon deposits; replace gasket if damaged. Spark arrestor screen: Clean with wire brush or replace if clogged.

CAUTION! Allow muffler to cool completely before handling. Do not operate without spark arrestor in wooded areas.

Disassembly & Reassembly

Major service procedures require special tools (piston stop, flywheel puller, clutch tool).

1. Cylinder/piston inspection: Remove muffler to view through exhaust port.
2. Crankcase splitting: Requires press or special tooling; not recommended without experience.
3. Clutch removal: Use STIHL clutch tool to hold drum, rotate clockwise to remove.
4. Flywheel removal: Use puller; do not hammer.

Note: Refer to detailed STIHL technical manual for full engine overhaul procedures.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	Fuel, spark, compression	Check fuel freshness, spark plug, decompression valve, carburetor settings.
Engine runs poorly/dies	Air filter, fuel filter, carburetor	Clean/replace air filter; replace fuel filter; service carburetor.
Chain doesn't turn	Clutch, sprocket, brake engaged	Inspect clutch springs/shoes; check sprocket; ensure chain brake disengaged.
Excessive vibration	AV mounts, unbalanced chain	Inspect anti-vibration buffers; balance chain; check crankshaft bearings.
Overheating	Dirty cooling fins, lean mixture	Clean fins; check carburetor H setting; verify fuel mix ratio.
Oil not lubricating	Oil pump, lines, bar hole	Check oil pump drive, lines for leaks, bar oil hole alignment.

Reset: For EMM system, disconnect battery (if equipped) for 30 seconds to reset.

Service: For genuine STIHL parts and technical support, contact authorized STIHL dealer or visit www.stihlusa.com.