Stihl Chainsaw Rebuild Manual

This manual provides comprehensive instructions for rebuilding a Stihl chainsaw. It covers safety precautions, required tools and parts, step-by-step disassembly and reassembly procedures, engine overhaul, fuel system servicing, bar and chain maintenance, troubleshooting common issues, and final testing. Always prioritize safety and refer to your specific Stihl model's technical data.

1. Safety First 2. Tools & Parts Required 3. Pre-Rebuild Inspection 4. Disassembly Procedure 5. Engine Overhaul 6. Fuel System Rebuild 7. Bar & Chain Service 8. Reassembly Guide 9. Post-Rebuild Testing 10. Maintenance Schedule 11. Troubleshooting

Safety First

Before beginning any work, ensure the chainsaw is completely cool, the spark plug wire is disconnected, and all fuel has been drained. Work in a clean, well-ventilated area.

Safety Item	Description
Personal Protective Equipment (PPE)	Wear safety glasses, cut-resistant gloves, and hearing protection.
Work Area	Clean, dry, and free of flammable materials or ignition sources.
Fuel Handling	Drain fuel into an approved container. No smoking.
Sharp Components	Handle the chain and guide bar with extreme care; use a chain guard.
Fasteners	Note torque specifications; do not overtighten.

Tools & Parts Required

Gather all necessary tools and replacement parts before starting.

Tools: Stihl-compatible socket set, torx bits, feeler gauges, piston ring compressor, circlip pliers, torque wrench, compression tester, carburetor adjustment tools.
Common Parts: Piston & ring set, cylinder (if scored), crankshaft seals, fuel lines, fuel filter, air filter, spark plug, carburetor rebuild kit, bar and chain (if worn).
Consumables: High-quality 2-stroke oil, bar oil, thread locker, gasket sealant, clean rags.

WARNING! Use only genuine Stihl or OEM-equivalent parts to ensure proper fit and performance.

Pre-Rebuild Inspection

Assess the saw's condition to determine the full scope of work needed.

Compression Test: Record reading. Below 110 psi often indicates need for top-end rebuild.
Visual Inspection: Check for cracked plastics, damaged bar, worn sprocket, and fuel leaks.
Functional Check: Note starting issues, idle problems, loss of power, or excessive smoke.
Disassembly Plan: Based on inspection, create a list of components to be replaced or serviced.

CAUTION! Document the disassembly process with photos or notes to aid reassembly.

Disassembly Procedure

Step 1 - External Components: Remove bar, chain, side cover, and clutch assembly.
Step 2 - Top Handle & Tank: Remove handle screws, separate fuel tank from engine housing.
Step 3 - Engine Access: Remove muffler, carburetor, intake manifold, and ignition coil.
Step 4 - Cylinder & Piston: Remove cylinder bolts, carefully lift cylinder off piston.
Step 5 - Crankcase: Split crankcase halves (if necessary for bearing/seal replacement).
Step 6 - Fuel System: Remove fuel tank, lines, filter, and pump (if equipped).

Engine Overhaul

Focus on the powerhead's core components.

Cylinder & Piston: Inspect cylinder walls for scoring. Light honing may be possible; deep scratches require replacement. Check piston for scuffing and ring groove wear. Replace rings and wrist pin clips.

Crankshaft & Bearings: Check crankshaft for straightness and bearing smoothness. Replace crankcase seals as a matter of course during any rebuild.

Ignition: Test coil with a spark tester. Ensure flywheel key is not sheared.

Fuel System Rebuild

A clean, airtight fuel system is critical for performance.

Dismantle carburetor using a rebuild kit. Soak metal parts in cleaner, replace diaphragms, gaskets, and needle valve.
Replace all fuel lines, filter, and tank vent. Inspect fuel cap.
Pressure/vacuum test the system after reassembly to check for leaks.

Tip: Use a diagram for carburetor reassembly. Set factory-preset adjustment screws to initial settings.

Bar & Chain Service

Even with an engine rebuild, the cutting system must be in good order.

Guide Bar: Clean bar groove, check for straightness and wear. Dress rails with a flat file if uneven. Rotate bar regularly to promote even wear.
Chain: Sharpen cutters to correct angle with a round file and guide. Ensure depth gauges are properly filed down.
Sprocket: Inspect drive sprocket (rim or spur) for wear; replace if teeth are hooked.
Lubrication: Clean oiler ports and ensure the automatic oiler is functioning.

WARNING! A dull or damaged chain is dangerous and increases kickback risk. Always wear gloves.

Reassembly Guide

Reverse the disassembly process, using new gaskets and seals.

Bottom End: If split, reassemble crankcase halves with sealant on mating surfaces. Torque bolts in a crisscross pattern to specification.
Piston & Cylinder: Lubricate piston and rings. Use a ring compressor to carefully install cylinder. Torque cylinder nuts evenly.
External Components: Reinstall carburetor, intake, muffler, ignition, fuel tank, and handle.
Final Connections: Connect all fuel lines, throttle linkage, and choke controls. Adjust linkage as needed.

CAUTION! Do not force components. Ensure all linkages move freely before final tightening.

Post-Rebuild Testing

Break-in procedure and operational check.

Pre-Start: Fill with proper fuel/oil mix and bar oil. Prime carburetor.
Start & Idle: Start saw, allow to warm up. Adjust idle speed screw so chain does not move.
Break-In: Run saw at varying loads (not full throttle) for first 2-3 tanks of fuel. This allows rings to seat.
Performance Check: Verify smooth acceleration, strong cutting power, and no abnormal noises or leaks.

Maintenance Schedule

To extend the life of your rebuild, adhere to regular maintenance.

Interval	Task
Before Each Use	Check chain tension, sharpness, and lubrication. Inspect for loose fasteners.
Every 10 Hours	Clean air filter, check spark plug condition.
Every 20 Hours	Clean cooling fins, check fuel filter.
Every Season	Deep clean, inspect bar and sprocket, replace fuel lines if stiff/cracked.
Annually	Check cylinder compression, crankcase seals.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Won't Start	No spark, flooded, fuel issue	Check spark plug, coil gap, and air gap. Ensure fresh fuel, clean carburetor.
Runs but Dies	Clogged filter, faulty fuel line	Replace fuel filter and inspect/clean fuel pickup line in tank.
Loss of Power	Air leak, clogged muffler, poor compression	Pressure test engine. Clean spark arrestor screen in muffler.
Excessive Vibration	Unbalanced clutch, loose components	Check clutch drum and bearing. Tighten all engine and handle mounts.
Chain Oils Poorly	Clogged oiler, worn pump	Clean oil ports, check oil line, test oil pump output.

Final Note: For model-specific specifications and technical bulletins, consult official Stihl documentation or an authorized dealer.

Support: Stihl USA: 1-800-467-8445; www.stihlusa.com