Stihl MS290 Chainsaw Parts Manual

The Stihl MS290 Farm Boss® is a professional-grade chainsaw designed for demanding tasks like felling, limbing, and bucking. This parts manual provides detailed diagrams, part numbers, and ordering information for all components of the MS290 chainsaw, including the engine, fuel system, cutting attachment, ignition system, and housing. Below are key sections for safety, parts identification, ordering, assembly diagrams, and maintenance.

1. Features at a Glance 2. Safety Parts & Features 3. Engine Assembly Parts 4. Fuel System Parts 5. Cutting Attachment Parts 6. Ignition System Parts 7. Housing & Covers 8. Part Number Reference 9. Assembly Diagrams 10. Maintenance Schedule 11. Troubleshooting & Ordering

Features at a Glance

Key components: 56.5cc engine, STIHL Quickstop® inertia chain brake, Ematic™ lubrication system, side-access chain tensioner, anti-vibration system, and decompression valve.

Feature	Description
Engine Displacement	56.5 cc, 2-stroke engine
Power Output	3.4 bhp (2.5 kW)
Guide Bar Lengths	16", 18", 20" (standard options)
Fuel Tank Capacity	16.9 fl. oz. (500 ml)
Oil Tank Capacity	11.1 fl. oz. (330 ml)
Weight (powerhead)	13.2 lbs (6.0 kg)
Ignition System	Electronic, capacitor discharge (CDI)
Chain Brake	STIHL Quickstop® inertia-activated
Chain Lubrication	Ematic™ system with adjustable pump
Anti-Vibration	STIHL Advanced Damping System

Safety Parts & Features

Critical safety components must be inspected regularly and replaced if damaged.

Chain Brake Assembly: Includes brake band, handle, and activation mechanism.
Throttle Control Lockout: Prevents accidental throttle engagement.
Right-Hand Guard: Protects hand from chain breakage.
Chain Catcher: Helps stop a broken or derailed chain.
Muffler with Spark Arrestor: Reduces fire risk (required in some areas).

WARNING! Never operate a chainsaw with damaged or missing safety parts. Always wear appropriate PPE.

Engine Assembly Parts

Cylinder, piston, crankshaft, carburetor, and associated components.

Cylinder & Piston: Part numbers for cylinder, piston, rings, and wrist pin.
Crankshaft & Bearings: Main crankshaft assembly and crankcase bearings.
Carburetor: Complete carburetor assembly, gaskets, and adjustment screws.
Air Filter System: Filter element, cover, and pre-cleaner.
Muffler: Complete muffler assembly, gasket, and spark arrestor screen.

CAUTION! Engine disassembly requires special tools and expertise. Consult a STIHL servicing dealer.

Fuel System Parts

Fuel Tank: Tank assembly, cap, and vent.
Fuel Line: Supply line from tank to carburetor.
Fuel Filter: In-tank filter element.
Impulse Line: Connects crankcase to fuel pump.
Carburetor Repair Kit: Includes diaphragms, gaskets, needle valve.
Oil Pump: Automatic and adjustable chain oil pump assembly.
Oil Lines: Supply line from tank to pump and to bar pad.

Cutting Attachment Parts

Guide bar, chain, drive sprocket, clutch, and tensioning system.

Guide Bar: Roller-nose or solid-nose bars in various lengths. Chain: STIHL Oilomatic® chains in .325" pitch, .063" gauge. Drive Sprocket: Rim sprocket or spur sprocket assembly. Clutch: Centrifugal clutch drum, springs, and shoes. Tensioning System: Side-access adjuster, pin, and screw.

Ignition System Parts

Spark plug, ignition module, stop switch, and wiring.

Turn off chainsaw and disconnect spark plug boot before servicing.
Match part numbers exactly for ignition module (CDI unit).
Check wiring harness for cracks or breaks.

Tip: Use only STIHL-recommended spark plugs (e.g., BOSCH WSR6F).

Housing & Covers

Plastic housing components, covers, and handles.

Remove: Turn fuel valve to OFF, remove all fuel.
Identify: Top cover, rear handle, front handle, and tank housing.
Replace: Ensure all anti-vibration mounts are correctly seated.
Reassemble: Tighten all screws to specified torque.
Inspect: Check for cracks, especially in handle areas.
Fasteners: Use correct STIHL screws and washers.
Decals: Replacement safety and instruction decals.
AV Mounts: Rubber dampers for anti-vibration system.

WARNING! A cracked housing can compromise safety and must be replaced.

Part Number Reference

Common replacement parts with STIHL part numbers.

Assembly Diagrams

Exploded-view diagrams for major assemblies (engine, clutch, oil pump).

CAUTION! Diagrams are for reference. Proper assembly requires technical knowledge.

Maintenance Schedule

Daily: Check chain tension, sharpness, and lubrication. Clean air filter. Weekly: Check all nuts, bolts, and screws. Clean spark arrestor screen. Monthly: Inspect fuel lines, filters, and anti-vibration elements. Annually: Have unit serviced by a STIHL dealer for compression check and detailed inspection.

Troubleshooting & Ordering

Symptom	Possible Cause	Corrective Action / Part Needed
Engine won't start	Fuel, spark, compression	Check fuel filter/lines, spark plug, ignition module.
Chain doesn't turn	Clutch, sprocket, brake	Inspect clutch shoes/springs, drive sprocket, ensure brake is disengaged.
Poor lubrication	Oil pump, lines, bar groove	Check oil pump function, replace oil lines, clean bar groove.
Excessive vibration	AV mounts, balance	Replace worn anti-vibration mounts, check for bent crankshaft.
Air leak	Crank seals, gaskets	Replace crankshaft seals, cylinder base gasket, intake manifold gasket.

Ordering: Use exact STIHL part numbers from this manual. Contact an authorized STIHL dealer.

Service: For repairs beyond routine maintenance, take your MS290 to an authorized STIHL servicing dealer.