The MS 290 Stihl Farm Boss is a professional-grade chainsaw designed for demanding farm and ranch work. This teardown manual provides step-by-step instructions for disassembly, inspection, and reassembly of key components including the engine, fuel system, ignition, chain brake, and cutting assembly. Below are detailed sections covering safety, tools required, disassembly procedures, part identification, troubleshooting, and reassembly guidelines.
Before beginning any teardown procedure, ensure the chainsaw is completely powered off, cooled down, and the spark plug wire is disconnected to prevent accidental starting.
| Precaution | Description |
|---|---|
| Disconnect Spark Plug | Prevents accidental engine ignition during disassembly |
| Drain Fuel & Oil | Empty fuel and chain oil tanks to prevent spills and fire hazard |
| Wear Protective Gear | Use gloves and safety glasses to protect from sharp edges and debris |
| Work in Ventilated Area | Ensure proper airflow when handling fuel or cleaning chemicals |
| Secure Chainsaw | Use a vise or stable workbench to prevent movement during disassembly |
| Organize Parts | Use containers or trays to keep screws and small components organized |
| Handle Sharp Components | Exercise caution when removing chain, guide bar, and cutting attachments |
| Refer to Torque Specs | Use a torque wrench during reassembly to avoid over-tightening |
| Avoid Force | Do not force components; use appropriate tools to avoid damage |
| Check for Wear | Inspect all parts for excessive wear, cracks, or damage before reassembly |
Gather the necessary tools before starting the teardown process.
WARNING! Using incorrect tools can damage components. Ensure tools are in good condition.
Complete these steps before disassembling any components.
CAUTION! Failure to drain fluids may result in spills and contamination of work area.
Disassemble carburetor, fuel lines, filter, and tank.
Carburetor: Remove diaphragm, gaskets, needle valve, and jets. Clean with carburetor cleaner. Fuel Lines: Inspect for cracks, brittleness, or leaks. Replace if necessary. Fuel Filter: Remove from tank and check for clogging. Fuel Tank: Clean interior with solvent, rinse, and dry thoroughly. Primer Bulb: Check for cracks and ensure it holds pressure.
Remove flywheel, ignition coil, spark plug, and stop switch.
Tip: Label all wires before disconnection to ensure correct reassembly.
Supports safe operation and power transmission.
WARNING! The clutch has left-hand threads; turn clockwise to loosen. Wear gloves when handling sharp sprocket teeth.
Remove cutting attachments for inspection and maintenance.
Thoroughly inspect all disassembled parts. Clean with appropriate solvents and compressed air.
CAUTION! Use proper ventilation when using solvents. Wear gloves and eye protection.
Reverse disassembly steps, using new gaskets and seals. Refer to torque specifications: Cylinder bolts (10 Nm), Clutch (35 Nm), Flywheel nut (40 Nm). Apply thread locker where specified. Ensure all connections are secure and components move freely.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Engine won't start | Fuel system, ignition, compression | Check spark, fuel delivery, and compression (should be 110+ psi). |
| Loss of power | Clogged air filter, exhaust screen, carburetor | Clean or replace filter; remove carbon from muffler screen; rebuild carb. |
| Oil not pumping | Clogged oil passages, faulty pump | Clean oil ports; inspect pump gear and diaphragm; replace if damaged. |
| Chain brake not engaging | Worn brake band, dirty mechanism | Inspect band for wear; clean and lubricate pivot points. |
| Excessive vibration | Loose components, unbalanced flywheel | Check all mounts and fasteners; inspect flywheel for damage or debris. |
Reset: After reassembly, perform a functional test without the chain to ensure all systems operate correctly.
Service: For genuine Stihl parts and technical support, visit www.stihlusa.com or contact an authorized Stihl dealer.