STIHL MS 461 Service Manual

The STIHL MS 461 is a professional-grade chainsaw featuring a high-performance engine, advanced anti-vibration system, and STIHL QuickStop® inertia chain brake. This service manual provides detailed instructions for maintenance, troubleshooting, and repair procedures to ensure optimal performance and safety. Below are key sections covering safety, specifications, maintenance, troubleshooting, and parts information.

Features at a Glance

Key components: High-torque engine with decompression valve, STIHL QuickStop® inertia chain brake, anti-vibration system, side-access chain tensioner, tool-free air filter cover, and advanced electronic ignition.

Safety Information

Always wear appropriate PPE: helmet, eye protection, hearing protection, gloves, chainsaw chaps, and sturdy boots.

1. Before Starting: Check chain tension, sharpness, and lubrication. Ensure all guards are in place.
2. During Operation: Maintain secure footing. Keep bystanders at a safe distance. Never operate above shoulder height.
3. Chain Brake Test: Test function before each use by activating brake with wrist.
4. Fuel Safety: Use only STIHL MotoMix® or fresh fuel/oil mixture (50:1). Refuel in well-ventilated area with engine off and cool.

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

Technical Specifications

• Engine Type: Single cylinder, 2-stroke, air-cooled.
• Bore x Stroke: 50 mm x 39 mm (1.97 in x 1.54 in).
• Power Output: 4.4 kW (6.0 bhp) at 9,500 rpm.
• Maximum Engine Speed: 13,500 rpm.
• Idle Speed: 2,800 rpm.
• Fuel/Oil Ratio: 50:1 (STIHL HP Ultra or equivalent).
• Spark Plug: NGK BPMR 7A (gap 0.020 in / 0.5 mm).
• Ignition Air Gap: 0.30 mm (0.012 in).
• Carburetor: STIHL HD-12 with compensation diaphragm.
• Chain Pitch/Gauge: 3/8" or .404" / .063" (1.6 mm) or .058" (1.5 mm).

Maintenance Schedule

Access maintenance points via tool-free covers. Front Panel: Master Control Lever, Decompression Valve, Chain Tensioner.

Daily: Clean air filter, check chain tension/sharpness, inspect chain brake function, clean cooling fins, check all fasteners.

Weekly: Clean spark arrestor screen, check fuel filter, inspect anti-vibration elements, clean guide bar groove and oil holes.

Monthly: Clean carburetor air passage, check spark plug condition/gap, inspect fuel lines for cracks, check clutch drum and sprocket wear.

Annually: Replace fuel filter, check cylinder/piston through exhaust port, inspect ignition system components, professional servicing recommended.

Engine Service

Cylinder & Piston: Remove muffler to inspect for scoring. Use ring compressor for piston installation.

1. Disconnect spark plug wire and remove plug.
2. Remove engine cover and air filter assembly.
3. Remove carburetor and intake manifold.
4. Remove cylinder bolts and carefully lift cylinder.
5. Inspect piston, rings, and cylinder walls for wear/scoring.
6. Replace components as needed using STIHL genuine parts.
7. Reassemble in reverse order, torque cylinder bolts to specification.

Torque Specs: Cylinder bolts: 10 Nm (88 in-lb). Spark plug: 25 Nm (18 ft-lb).

Fuel System

Carburetor Adjustment: Requires special STIHL adjustment tool. Initial settings: L screw - 1 turn open, H screw - 1 turn open.

1. Clean external surfaces before disassembly.
2. Remove carburetor cover and disconnect fuel/impulse lines.
3. Disassemble carburetor, clean all parts in solvent.
4. Replace diaphragms, gaskets, and filter screen.
5. Reassemble and adjust at operating temperature.
6. Final adjustment: Set H screw for maximum speed (13,500 rpm), then rich 1/8 turn. Set L screw for smooth idle and acceleration.

Tip: Always use pressure/vacuum tester to check crankcase seals after carburetor service.

Ignition System

Electronic ignition module: Check resistance values with multimeter.

1. Remove spark plug and check for spark (ground electrode to cylinder).
2. Check spark plug gap: 0.5 mm (0.020 in).
3. Measure ignition coil primary resistance: 0.18-0.27 ohms.
4. Measure secondary resistance: 4.5-6.5 kΩ.
5. Check stop switch continuity: Should be open when off, closed when on.
6. Inspect flywheel key for shearing; check air gap: 0.30 mm (0.012 in).

WARNING! Never crank engine with spark plug disconnected and wire grounded - can damage ignition module.

Chain & Bar Maintenance

Chain Sharpening: Use round file matching chain pitch (typically 5.5 mm / 7/32" for 3/8" chain).

1. Secure bar in vise. File at 30° angle, maintaining cutter height consistency.
2. File depth gauges with flat file and gauge tool (0.025" / 0.65 mm below cutter tip).
3. Clean bar groove with bar groove cleaner tool.
4. Check bar for straightness and wear; dress rails with flat file if uneven.
5. Lubricate sprocket nose bearing regularly.
6. Rotate bar 180° daily for even wear.

Chain Tension: Correct when chain snaps back after pulling from bar with light resistance.

Cooling & Exhaust System

Clean cooling fins weekly; remove carbon from exhaust port and spark arrestor screen.

CAUTION! Allow engine to cool completely before servicing exhaust system.

Troubleshooting Guide

Compression Test: Minimum 100 psi for starting, 120+ psi for good performance.

Parts Diagrams

Refer to STIHL illustrated parts catalog for MS 461. Key assemblies: Engine group, Fuel system, Ignition, Clutch/Drive, Chain brake, Anti-vibration, Covers/handles.

Ordering Parts: Use STIHL part numbers from diagrams. Common replacement parts: Piston kit (1128 030 2005), Cylinder (1128 030 2003), Carburetor kit (1128 007 1067), Ignition module (1128 400 1301).

Service Support: Authorized STIHL dealers only. Visit www.stihlusa.com or contact 1-800-467-8445 for dealer locator.