The STIHL Farm Boss is a professional-grade chainsaw designed for demanding farm and forestry work. This service manual provides comprehensive information for maintenance, troubleshooting, and repair of the STIHL Farm Boss series chainsaws. Below are key sections covering safety, specifications, maintenance procedures, troubleshooting, and parts information.
Always follow safety guidelines to prevent injury and equipment damage.
| Safety Area | Precaution |
|---|---|
| Personal Protective Equipment | Wear safety glasses, hearing protection, gloves, chainsaw chaps, and steel-toed boots |
| Work Area Safety | Clear work area of obstacles; ensure secure footing; maintain safe distance from others |
| Chain Brake | Test chain brake before each use; engage when carrying saw |
| Fuel Handling | Use approved fuel containers; refuel in well-ventilated area away from ignition sources |
| Kickback Prevention | Hold saw firmly with both hands; avoid contact with bar nose; use reduced-kickback chain |
| Maintenance Safety | Disconnect spark plug before performing maintenance; allow engine to cool |
| Starting Procedure | Place saw on ground; secure with foot in rear handle; use proper starting technique |
| Cutting Techniques | Plan cuts carefully; be aware of falling hazards; never cut above shoulder height |
| Transport & Storage | Engage chain brake; empty fuel tank for long-term storage; store in dry location |
| Emergency Procedures | Know how to stop engine quickly; have first aid kit available |
Regular maintenance ensures optimal performance and longevity.
WARNING! Always use genuine STIHL parts for maintenance. Improper parts can void warranty and cause safety hazards.
Proper engine maintenance is critical for performance and reliability.
Cylinder and Piston: Inspect for scoring through exhaust port. Compression should be 120-150 psi. Replace if below 100 psi.
Carburetor Adjustment: Factory settings: L screw 1 turn out, H screw 1 turn out. Fine-tune for optimal performance at operating temperature.
Ignition Timing: Fixed timing on most models. Check flywheel key if engine timing appears incorrect.
Cooling System: Keep cooling fins clean. Overheating causes engine damage.
Decompression Valve: Test for leaks. Replace if engine is hard to start or loses compression.
The fuel system requires proper mixture and clean components.
CAUTION! Never use automotive oil or incorrect fuel mixture. This causes engine damage and voids warranty.
Electronic ignition provides reliable spark with minimal maintenance.
| Component | Test Procedure | Specification |
|---|---|---|
| Spark Plug | Check gap (0.020"), clean electrodes, replace if worn | NGK BPMR7A or equivalent |
| Ignition Module | Check for spark with tester; inspect for physical damage | Spark should jump 1/4" gap |
| Flywheel | Check magnets; inspect keyway; clean contact surfaces | No cracks; magnets intact |
| Stop Switch | Test continuity; ensure proper ground when engaged | Open circuit when off |
| Wiring Harness | Inspect for fraying, cuts, or poor connections | No damage; secure connections |
Note: Most ignition failures are due to faulty spark plugs or loose connections.
Proper chain and bar care ensures cutting efficiency and safety.
WARNING! Dull chains increase kickback risk and cause premature wear.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Engine won't start | No spark, flooded, fuel issues | Check spark plug; clear flood; verify fuel flow and mixture |
| Engine starts then dies | Fuel filter clogged, carburetor issues | Replace fuel filter; clean carburetor; check tank vent |
| Poor performance | Dirty air filter, exhaust blocked | Clean/replace air filter; clean spark arrestor screen |
| Chain won't turn | Clutch worn, sprocket damaged | Inspect clutch springs and shoes; replace sprocket |
| Excessive vibration | Loose components, unbalanced chain | Tighten all fasteners; balance chain; check anti-vibration mounts |
| Chain throws oil | Over-oiling, wrong oil viscosity | Adjust oiler; use proper chain oil; clean oil passages |
| Engine overheats | Dirty cooling fins, lean mixture | Clean cooling fins; check carburetor adjustment; verify fuel mixture |
| Hard starting when hot | Ignition coil failing, decompression valve leak | Test ignition coil; replace decompression valve |
| Chain won't stay tight | Worn bar, stretched chain | Inspect bar for wear; replace chain if stretched beyond adjustment |
| Loss of power under load | Compression loss, fuel restriction | Check compression; inspect fuel system; clean carburetor |
Refer to official STIHL parts diagrams for exact part numbers and assembly.
Note: Always use STIHL part numbers when ordering replacements.
STIHL Farm Boss chainsaws come with limited warranty coverage.
Important: Warranty may be void if non-STIHL parts are used or if maintenance is neglected.
For technical assistance and service information:
Emergency Contact: For immediate safety concerns, contact your local STIHL dealer.