2010 STIHL MS 261, MS 261 C Chainsaw Service Manual & Parts Lists (P/N 0455 573 0123)

This May 2010 STIHL service manual covers the MS 261 and MS 261 C chainsaws, with illustrated parts lists for matching components to the covered variants. The appended MS 270, MS 270 C, MS 280 and MS 280 C material provides parts identification only; the repair procedures apply to the MS 261 family.

• Engine repair: Crankcase pressure and vacuum testing, cylinder and piston service, crankshaft removal and installation, bearing replacement, and oil-seal replacement.

• Fuel system: Carburetor leakage testing, diaphragm and inlet-needle service, basic and standard adjustments, tank-vent testing, and manual fuel-pump replacement.

• Clutch and chain brake: Clutch inspection, brake-band and brake-lever replacement, QuickStop Super cable adjustment, and standard and quick chain-tensioner service.

• Chain lubrication: Oil-supply troubleshooting, pickup-body and suction-hose inspection, oil-pump removal and replacement, and oil-tank valve service.

• Starter and handle assemblies: Rewind-starter and ErgoStart repairs, starter-rope replacement, AV spring and buffer service, handlebar replacement, and control-lever repairs.

• Ignition and heating: Spark testing, stop-circuit checks, ignition troubleshooting charts, heating-system circuit diagrams, and component resistance tests.

STIHL specifies this service manual for properly equipped repair shops, including the specialist tools and test equipment required for the documented work.

Engine Rebuilding and Workshop Tools

The engine section distinguishes oil-seal replacement without engine disassembly from crankshaft removal and crankcase separation. It also identifies the crankshaft, connecting rod and needle bearing as an inseparable replacement assembly.

Cylinder installation guidance addresses the risk of breaking piston rings if they project beyond the cylinder wall. Illustrated crankcase views and bearing-installation instructions show the assembly relationships involved in internal engine repairs.

Tool references include assembly stand 5910 890 3101, carburetor and engine tester 0000 850 1300, and dedicated installing and press sleeves for the oil seals.

Carburetor Variants and Fuel-System Diagnosis

The parts list assigns C1Q-S178 carburetors to standard and QuickStop Super versions, C1Q-S179 to the C-BE, and C1Q-S180 to heated versions. These assignments help match the carburetor assembly to the saw's equipment before selecting replacement parts.

Basic adjustment after limiter-cap removal is distinguished from standard adjustment with the cap installed. The limiter-cap section also warns that excessive puller engagement can damage the high-speed adjusting screw.

Fuel-system diagnosis covers the inlet needle, metering and pump diaphragms, intake manifold and tank vent. The chain-lubrication troubleshooting table distinguishes pickup, hose, vent and worm-drive faults from oil-pump failures.

QuickStop Super and Starting Equipment

QuickStop Super coverage links coasting-brake symptoms to brake-cable condition and interlock-lever free travel. Separate illustrations cover its brake lever, cable retainer and throttle-control arrangement.

The starter section differentiates standard, ElastoStart and ErgoStart components. It also explains why the longer-base flywheel puller 5910 890 4504 is required for ErgoStart versions.

Ignition and Heating-Circuit Fault Finding

The Ignition System Troubleshooting chart supports spark, wiring and stop-switch diagnosis. ZAT 3 and ZAT 4 tester procedures check spark output; ignition timing is fixed and is not adjustable during repair.

Heated versions have a Carburetor Heating System Troubleshooting Chart, a Handle Heating and Generator Troubleshooting Chart, and a circuit diagram identifying the generator, switches and heating elements. The Test Connections and Test Values tables connect resistance readings with component faults.

The rear-handle heating element is replaceable, while a failed element inside the front handle requires replacement of the handlebar assembly. Ignition testing involves high voltage and possible engine startup; the manual's safety precautions apply to these tests.

Sample Ignition, Carburetor and Clutch Specifications

These examples are a small selection of the manual's adjustment, testing and fastener data.

The ignition-module-to-fanwheel air gap is 0.20 mm (+0.10/-0.05 mm). Carburetor leakage testing uses approximately 0.8 bar (80 kPa), with pressure retention used to assess sealing.

The torque table specifies 50 Nm for the clutch carrier-to-crankshaft connection and supplies separate values and fastener notes for other assemblies.

Searchable Text, Bookmarks and PDF Contents

Search and diagram detail: Service text and parts tables are searchable, with embedded bookmarks for service sections and appended catalogs. Some MS 261 exploded-view callouts are outside the searchable text layer. Heating-circuit labels are readable, with enlargement available for small details.

One printable, 335-page PDF contains the 151-page service manual, including its front and back covers; a 32-page MS 261/MS 261 C parts list; and four identical copies of the 38-page MS 270/280 family parts list, totaling 152 pages. All covers, appended material and duplicate pages are already included in the 335-page total.