STIHL MS290 Repair Manual PDF

The STIHL MS290 Farm Boss® is a professional-grade chainsaw featuring a 56.5 cc engine, STIHL Quickstop® inertia chain brake, Ematic™ lubrication system, and anti-vibration system. This repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair procedures. Below are key sections covering safety, specifications, maintenance schedules, common repairs, and troubleshooting.

1. Safety Information 2. Specifications 3. Maintenance Schedule 4. Engine Repair 5. Fuel System 6. Ignition System 7. Chain & Bar Maintenance 8. Clutch & Sprocket 9. Anti-Vibration System 10. Troubleshooting Guide 11. Parts Diagram

Safety Information

Always wear appropriate PPE: safety glasses, hearing protection, gloves, chainsaw chaps, and sturdy boots. Ensure chain brake is functional before operation.

Safety ComponentDescription
Chain BrakeSTIHL Quickstop® inertia-activated; stops chain within milliseconds
Right-Hand GuardProtects hand from chain if it breaks or derails
Throttle InterlockPrevents accidental throttle activation
MufflerReduces noise and directs exhaust away from operator
Chain CatcherHelps reduce risk of chain hitting operator if it breaks

Specifications

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

  1. Before Each Use: Check chain tension, sharpness, and lubrication; inspect for loose fasteners.
  2. Every 5 Hours: Clean air filter; check spark plug.
  3. Every 10 Hours: Clean spark arrestor screen; inspect fuel filter.
  4. Every 20 Hours: Replace fuel filter; clean cooling fins.
  5. Every 50 Hours: Replace spark plug; clean carburetor.
  6. Annually: Replace air filter; inspect anti-vibration mounts.

WARNING! Always disconnect spark plug wire before performing maintenance.

Engine Repair

Common engine repairs include cylinder/piston inspection, crankshaft bearing replacement, and decompression valve service.

  1. Remove engine cover and muffler.
  2. Inspect cylinder for scoring; hone if necessary.
  3. Check piston rings for wear; replace if gap exceeds 0.35 mm.
  4. Inspect crankshaft bearings for play; replace if worn.
  5. Reassemble with new gaskets; torque cylinder bolts to 10 Nm (88 in-lb).

CAUTION! Use genuine STIHL parts for optimal performance.

Fuel System

Components: fuel tank, filter, lines, carburetor (Walbro WT-426).

  1. Drain fuel before servicing.
  2. Replace fuel filter annually or if clogged.
  3. Clean carburetor: disassemble, soak in cleaner, blow out passages.
  4. Adjust carburetor: LA screw 1 turn out; H screw 1¼ turns out (baseline).
  5. Inspect fuel lines for cracks; replace if brittle.

Tip: Use fresh 50:1 fuel mix (STIHL HP Ultra oil recommended).

Ignition System

Electronic ignition module; no points to adjust.

  1. Check spark: remove plug, ground to cylinder, pull starter.
  2. If no spark, test ignition coil with multimeter (primary 0.5-1.5 Ω, secondary 8-15 kΩ).
  3. Replace coil if out of spec.
  4. Check stop switch wire for continuity to ground.
  5. Ensure flywheel key is not sheared.

WARNING! High voltage risk; handle ignition components carefully.

Chain & Bar Maintenance

Proper chain maintenance ensures safe and efficient cutting.

  1. Sharpen chain regularly with round file (4.0 mm for 3/8" pitch).
  2. File cutters at 30° angle; maintain depth gauges (0.025" below cutter).
  3. Rotate bar weekly to ensure even wear.
  4. Clean bar groove and oil holes.
  5. Adjust chain tension: snug against bar, pull to check free movement.

CAUTION! Always wear gloves when handling chain.

Clutch & Sprocket

Centrifugal clutch engages at approximately 2,800 RPM.

  1. Remove clutch cover and bar/chain.
  2. Use clutch removal tool to unscrew clutch (left-hand threads).
  3. Inspect clutch shoes for wear; replace if worn more than 50%.
  4. Replace sprocket if teeth are hooked or worn.
  5. Reassemble; torque clutch nut to 40 Nm (30 ft-lb).

Anti-Vibration System

Reduces vibration transmitted to handles via rubber mounts.

  1. Inspect front and rear AV mounts for cracks or deterioration.
  2. Replace mounts if damaged: remove handle screws, extract old mounts.
  3. Install new mounts; torque handle bolts to 10 Nm (88 in-lb).
  4. Check AV springs in tank housing for fatigue.

Troubleshooting Guide

SymptomPossible CauseCorrective Action
Engine won't startNo spark, flooded, fuel issueCheck spark plug; dry plug; clean carburetor; fresh fuel.
Engine runs poorlyClogged air filter, dirty carbClean/replace air filter; service carburetor.
Chain won't turnClutch worn, sprocket damagedInspect clutch shoes; replace sprocket.
Excessive vibrationAV mounts damaged, loose fastenersReplace AV mounts; tighten all bolts.
Chain oil not flowingClogged oil passages, pump failureClean oil holes; inspect oil pump drive.

Reset: For electronic issues, disconnect spark plug wire for 30 seconds.

Parts Diagram

Refer to official STIHL MS290 IPL (Illustrated Parts List) for part numbers and exploded views. Key assemblies: Engine Group (1128), Fuel System (1140), Ignition (1139), Clutch & Sprocket (1154), AV System (1119).

Service: For technical support, contact STIHL at 1-800-467-8445 or visit www.stihlusa.com.

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