Stihl Chainsaw Rebuild Manual

The Stihl Chainsaw Rebuild Manual provides comprehensive guidance for disassembling, inspecting, repairing, and reassembling Stihl chainsaw engines and components. This manual covers essential safety protocols, required tools, step-by-step procedures for engine overhaul, fuel system servicing, ignition system troubleshooting, bar and chain maintenance, and performance testing. Below are key sections for safety, tools, procedures, specifications, and troubleshooting.

1. Safety Precautions 2. Required Tools & Equipment 3. Engine Disassembly 4. Cylinder & Piston Inspection 5. Crankshaft & Bearings 6. Fuel System Rebuild 7. Ignition System 8. Reassembly Procedures 9. Bar & Chain Maintenance 10. Performance Testing 11. Troubleshooting

Safety Precautions

Critical safety measures before starting any rebuild work.

Precaution	Description
Work Area	Clean, well-ventilated space free of flammable materials
Personal Protective Equipment (PPE)	Safety glasses, gloves, hearing protection
Fuel Handling	Drain fuel tank completely; work in ventilated area
Sharp Edges	Handle cutting chain and bar with extreme care
Electrical Safety	Disconnect spark plug wire before disassembly
Component Handling	Use proper tools; avoid forcing parts
Cleanliness	Keep work area and parts clean to prevent contamination
Documentation	Take photos during disassembly for reference

Required Tools & Equipment

Essential tools for Stihl chainsaw rebuild.

Stihl specialty tools: Piston stop, flywheel puller, clutch removal tool.
Standard tools: Metric socket set, torque wrench, screwdrivers, pliers.
Measuring tools: Feeler gauges, caliper, compression tester.
Cleaning supplies: Parts cleaner, brushes, compressed air.
Replacement parts: Gasket kit, piston rings, bearings, seals.

WARNING! Use only Stihl-approved tools for specific components to avoid damage.

Engine Disassembly

Step-by-step engine teardown procedure.

Remove external components: Bar, chain, air filter, spark plug, muffler.
Drain fluids: Fuel and bar/chain oil.
Remove top cover and handle assembly.
Disconnect carburetor and fuel lines.
Remove clutch assembly using clutch tool.
Remove flywheel using puller tool.
Separate crankcase halves after removing all fasteners.

CAUTION! Label all parts and fasteners; organize in order of removal.

Cylinder & Piston Inspection

Cylinder Walls: Check for scoring, scratches, or wear. Measure bore diameter.
Piston: Inspect skirt for wear; check ring grooves for carbon buildup.
Piston Rings: Check end gap; replace if worn or broken.
Cylinder Head: Inspect for cracks; check mating surface flatness.
Compression Test: Perform before and after rebuild (minimum 110 PSI).
Decarbonizing: Remove carbon deposits from piston crown and exhaust port.

Crankshaft & Bearings

Inspect crankshaft journals for wear or scoring. Check connecting rod play (side-to-side and up-down). Replace main bearings if rough or noisy. Inspect seals for leaks; always replace during rebuild. Ensure proper alignment during reassembly.

Measurements: Crankshaft runout (max 0.002"), connecting rod big-end play (spec: 0.004-0.008").

Fuel System Rebuild

Carburetor overhaul: Disassemble, clean all passages, replace diaphragm, gaskets, and filter. Fuel lines: Replace all lines and filter. Fuel tank: Clean interior, check for cracks. Pressure/vacuum test system after reassembly.

Remove carburetor and disassemble completely.
Soak metal parts in carburetor cleaner.
Replace all soft parts in rebuild kit.
Adjust mixture screws to factory settings.

Tip: Use only ethanol-free fuel to prevent carburetor issues.

Ignition System

Test spark plug: Replace if electrodes worn. Check ignition coil: Resistance test (primary: 0.5-2.0Ω, secondary: 8-15kΩ). Inspect flywheel: Check magnets, keyway, and condition. Test kill switch circuit. Ensure proper spark plug gap (0.020").

WARNING! Never crank engine with spark plug removed and wire grounded against cylinder.

Reassembly Procedures

Reverse of disassembly with specific torque values.

Install new crankshaft seals and bearings.
Assemble crankcase halves with new gasket; torque bolts in crisscross pattern.
Install piston with arrow facing exhaust port; use ring compressor.
Install cylinder; ensure rings don't catch on ports.
Torque cylinder bolts to specification (typically 10-12 Nm).
Install flywheel with woodruff key; torque nut (35-40 Nm).
Install clutch with proper tool; torque (25-30 Nm).
Reassemble fuel system with new lines.

CAUTION! Apply appropriate sealants; don't overtighten fasteners.

Bar & Chain Maintenance

Inspect bar for straightness, groove wear, and sprocket nose condition. Dress bar rails if uneven. Sharpen chain: Maintain correct angle (30°), depth gauge setting. Lubrication: Clean oil passages, adjust oil pump output. Chain tension: Proper sag (1/4" pull from bar).

Performance Testing

After rebuild: Start engine, check for leaks. Adjust carburetor: Idle, low speed, high speed. Test acceleration and maximum RPM. Check oiler function. Verify chain brake operation. Final inspection: All fasteners tight, covers installed, safety features functional.

Run-in Period: Operate at varying loads for first tank of fuel; avoid extended full throttle.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No start after rebuild	Fuel delivery, spark, compression	Check fuel lines, spark, compression (min 110 PSI)
Poor performance	Air leak, carb adjustment	Pressure test crankcase; adjust carburetor
Excessive vibration	Imbalance, misalignment	Check flywheel/clutch balance; crankshaft alignment
Overheating	Lean mixture, cooling fins	Rich-en mixture; clean cooling fins
Oil leakage	Seal failure, gasket	Replace seals/gaskets; check mating surfaces
Chain won't oil	Clogged passages, pump	Clean oil passages; check pump operation

Technical Support: Stihl dealer network or 1-800-GO-STIHL.

Parts: Use only genuine Stihl replacement parts.