STIHL MS 271 Repair Manual
The STIHL MS 271 is a mid-range, professional-grade chainsaw designed for demanding tasks such as felling, limbing, and bucking. This repair manual provides comprehensive instructions for troubleshooting, maintenance, disassembly, and reassembly of the MS 271. It covers the engine, fuel system, ignition system, chain brake, clutch, guide bar, and cutting chain. Below are key sections for safety, specifications, troubleshooting, step-by-step repair procedures, and parts identification.
Safety Precautions
Before performing any repair, ensure the chainsaw is turned off, the spark plug boot is disconnected, and all moving parts have stopped. Wear appropriate personal protective equipment (PPE).
| Hazard | Precaution |
|---|
| Fuel Fire/Explosion | Work in well-ventilated area; no smoking or open flames. |
| Accidental Start-up | Disconnect spark plug wire before any repair. |
| Sharp Chain | Always wear cut-resistant gloves; engage chain brake when not cutting. |
| Hot Surfaces | Allow engine and muffler to cool before handling. |
| Toxic Fumes | Operate and test only in open, ventilated spaces. |
Specifications & Technical Data
- Engine: STIHL 2-MIX engine, 50.2 cc displacement.
- Power Output: 3.0 bhp (2.2 kW).
- Fuel Tank Capacity: 16.9 fl. oz. (500 ml).
- Oil Tank Capacity: 11.8 fl. oz. (350 ml).
- Guide Bar Lengths: 16", 18", 20" (standard).
- Chain Pitch/Gauge: 3/8" PMM, .050" (1.3 mm).
- Idle Speed: 2,800 RPM.
- Maximum Power Speed: 13,000 RPM.
- Ignition System: Electronic, capacitor discharge.
- Weight (powerhead): 12.1 lbs (5.5 kg).
Troubleshooting Guide
Use this guide to diagnose common MS 271 problems before disassembly.
| Symptom | Possible Cause | Corrective Action |
|---|
| Engine fails to start | No spark, flooded engine, clogged fuel filter, stale fuel | Check spark plug; replace if fouled. Use fresh fuel mix (50:1). Clean/replace fuel filter. |
| Engine starts then dies | Clogged carburetor, faulty ignition coil, air leak | Clean carburetor jets. Check coil air gap (0.3 mm). Inspect intake boot and crankshaft seals. |
| Loss of power | Clogged air filter, muffler spark arrestor, fuel line crack | Clean air filter. Remove and clean spark arrestor screen. Inspect fuel lines for cracks. |
| Chain does not turn | Worn clutch, damaged sprocket, improper chain tension | Inspect clutch shoes and drum for wear. Replace if worn. Adjust chain tension. |
| Excessive vibration | Loose components, unbalanced chain, damaged AV mounts | Tighten all fasteners. Sharpen and balance chain. Inspect anti-vibration mounts. |
| Oil not feeding to bar | Clogged oiler holes, faulty oil pump, empty oil tank | Clean oil passages. Test oil pump output. Ensure oil tank is filled with STIHL chain oil. |
Maintenance Schedule
Regular maintenance is critical for performance and safety.
- Before Each Use: Check chain tension and sharpness; inspect for loose fasteners; verify throttle trigger and chain brake function.
- Every 10 Hours: Clean air filter; check spark plug condition; clean exterior of saw.
- Every 20 Hours: Clean spark arrestor screen; inspect fuel filter and lines; check clutch and sprocket for wear.
- Every 50 Hours: Replace fuel filter; clean carburetor (if needed); inspect anti-vibration elements.
- Every 100 Hours: Replace spark plug; inspect piston through exhaust port; check all gaskets and seals.
CAUTION! Use only genuine STIHL parts and specified lubricants.
Engine System Repair
Procedures for cylinder, piston, and crankshaft service.
- Remove Cylinder: Remove muffler and carburetor. Unbolt cylinder base nuts. Carefully lift cylinder off.
- Piston Inspection: Check piston for scoring, ring groove wear, and pin bearing play. Replace if damaged.
- Crankshaft Seal Replacement: Remove clutch and flywheel. Pry out old seals. Press new seals flush with case.
- Reassembly: Lubricate piston and rings with 2-stroke oil. Align ring gaps with piston pins. Torque cylinder nuts to specification.
WARNING! Label all parts during disassembly. Do not scratch cylinder bore.
Fuel System Repair
Servicing carburetor, fuel lines, tank, and filter.
- Carburetor Removal: Disconnect fuel line and impulse line. Remove throttle linkage. Unbolt carburetor.
- Carburetor Cleaning: Disassemble diaphragm covers. Clean all jets and passages with compressed air. Replace diaphragms and gaskets.
- Fuel Line Replacement: Remove tank housing. Pull old lines out. Insert new lines, ensuring proper routing to carburetor and filter.
- Fuel Filter: Replace filter by pulling from inside tank. Use a weighted filter for consistent fuel flow.
Tip: Always pressure and vacuum test the fuel system after repair.
Ignition System Repair
Testing and replacing ignition coil, spark plug, and stop switch.
- Spark Test: Remove spark plug, reconnect boot, ground plug against cylinder. Pull starter; look for strong blue spark.
- Coil Air Gap: Set gap between coil legs and flywheel magnets to 0.3 mm (0.012 in).
- Coil Replacement: Remove flywheel (use puller). Unbolt old coil. Install new coil and set air gap.
- Stop Switch Test: Use multimeter to check for continuity when switch is pressed. Replace if open circuit.
Note: Weak spark often indicates a faulty coil or improper gap.
Chain Brake & Clutch Repair
Servicing the chain brake band, clutch assembly, and sprocket.
- Chain Brake Disassembly: Remove side cover and bar. Remove brake band pivot pin. Inspect band for wear or distortion.
- Clutch Removal: Hold piston with rope in spark plug hole. Use clutch tool to remove clutch nut and clutch assembly.
- Clutch Inspection: Check shoes for wear and springs for fatigue. Replace if shoes are worn beyond service limit.
- Sprocket Replacement: Remove clutch drum. Replace rim sprocket or spur sprocket if teeth are hooked or worn.
CAUTION! The clutch spring is under tension; wear eye protection during removal.
Guide Bar & Chain Maintenance
Proper care to extend bar and chain life.
- Bar Cleaning: Remove bar and clean oil grooves and guide slot with a narrow wire. File down any burrs on rails.
- Bar Rotation: Flip bar weekly to ensure even wear on both rails.
- Chain Sharpening: Use correct round file size (5.5 mm for 3/8" PMM). Maintain proper filing angle (30°). Keep all cutters uniform length.
- Depth Gauge Setting: Use a depth gauge tool to set rakers 0.025" (0.65 mm) below cutter top plate.
WARNING! A dull or improperly sharpened chain increases kickback risk.
Torque Specifications
Critical fastener torque values (use a calibrated torque wrench).
| Fastener | Torque | Notes |
|---|
| Cylinder nuts | 10 Nm (88 in-lb) | Apply in crisscross pattern |
| Muffler bolts | 8 Nm (71 in-lb) | Use anti-seize compound |
| Clutch nut | 40 Nm (30 ft-lb) | Right-hand thread |
| Flywheel nut | 40 Nm (30 ft-lb) | Use impact or hold piston |
| Guide bar nuts | 9 Nm (80 in-lb) | Snug evenly |
| Spark plug | 20 Nm (15 ft-lb) | Do not over-tighten |
Exploded Views & Parts List
Reference diagrams for ordering correct replacement parts.
- Group 1: Crankcase, Cylinder, Piston Assembly.
- Group 2: Fuel Tank, Handle, Anti-Vibration System.
- Group 3: Carburetor, Air Filter, Intake Manifold.
- Group 4: Ignition System, Flywheel, Starter Assembly.
- Group 5: Clutch, Chain Brake, Sprocket.
- Group 6: Guide Bar, Chain, Oil Pump.
- Group 7: Covers, Fasteners, Decals.
Parts Ordering: Always provide the saw's serial number and part number from the diagram. Contact an authorized STIHL dealer.
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