The STIHL MS 250 is a professional-grade chainsaw designed for demanding cutting tasks. This service manual provides detailed instructions for maintenance, troubleshooting, and repair of the MS 250 model. It covers engine specifications, fuel system, ignition system, chain brake, lubrication, and electrical components. Below are key sections for safety, specifications, maintenance procedures, troubleshooting, and parts identification.
Key components: STIHL 2-MIX engine, Quickstop® inertia chain brake, side-access chain tensioner, Ematic™ lubrication system, anti-vibration system, and decompression valve.
| Feature | Description |
|---|---|
| Engine Type | STIHL 2-MIX single-cylinder, two-stroke |
| Displacement | 45.4 cc (2.77 cu. in.) |
| Power Output | 2.6 kW (3.5 bhp) |
| Fuel Tank Capacity | 0.47 L (16 oz.) |
| Oil Tank Capacity | 0.26 L (8.8 oz.) |
| Guide Bar Lengths | 16" (40 cm) or 18" (45 cm) |
| Chain Pitch | 3/8" PMM3 |
| Weight (powerhead) | 5.2 kg (11.5 lbs) |
| Ignition System | Electronic, capacitor discharge (CDI) |
| Starter | STIHL Easy2Start™ system |
Always wear appropriate PPE: helmet, eye protection, hearing protection, gloves, chainsaw chaps, and sturdy boots.
WARNING! Risk of severe injury or death from kickback, chain contact, or falling objects. Never operate a damaged or improperly maintained chainsaw.
Access maintenance points via removal of covers and air filter. Daily: Check chain tension, sharpness, and lubrication. Weekly: Clean air filter, check spark plug. Monthly: Clean cooling fins, check fuel filter, inspect anti-vibration elements. Annually: Replace spark plug, clean carburetor, check cylinder compression.
Remote: Not applicable. Use appropriate STIHL tools (screwdrivers, socket set, compression gauge, feeler gauges).
Chain: Tension properly (lift chain from bar, slight resistance). Lubrication: Check oiler output. Engine: Adjust carburetor only with tachometer. Install: Use genuine STIHL parts for all replacements.
Cylinder & Piston: Inspect for scoring. Compression should be ≥ 120 psi. Carburetor Adjustment: LA screw (idle), H screw (high speed), L screw (low speed). Default: LA 1 turn open, H & L 1 turn open from lightly seated.
Tip: Mark screw positions before adjustment. Use STIHL diagnostic tool for electronic carburetor versions.
Supports 50:1 fuel mix. Tank capacity 0.47 L.
WARNING! Fuel is highly flammable. Work in well-ventilated area, away from sparks or open flame. Use approved fuel containers.
Spark Plug: Bosch WSR6F, gap 0.5 mm. Ignition Module: CDI unit, non-adjustable. Stop Switch: Test for continuity. Flywheel: Check key and magnets for damage.
Unplug spark plug boot before servicing chain. Sharpen chain regularly with round file and guide. Clean bar groove and oil holes. Rotate bar periodically for even wear.
CAUTION! Always wear cut-resistant gloves when handling chain. Ensure chain brake is disengaged during maintenance.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Engine won't start | No spark, fuel, or compression | Check spark plug, fuel freshness, fuel filter, compression. |
| Engine runs poorly | Clogged air filter, carb adjustment | Clean/replace air filter; adjust carburetor. |
| Chain doesn't oil | Clogged oiler, empty tank, worn pump | Clean oil passages; fill tank; inspect/replace oil pump. |
| Excessive vibration | Loose parts, worn AV mounts | Tighten all fasteners; replace anti-vibration elements. |
| Chain brake doesn't engage | Dirty mechanism, worn band | Clean brake components; replace band if worn. |
Reset: Not applicable. For electronic issues, replace CDI module.
Service: Authorized STIHL servicing dealers only. Use genuine STIHL parts.
Refer to official STIHL MS 250 IPL (Illustrated Parts List) for exploded views and part numbers. Common replacement parts: air filter (1140 140 1605), spark plug (WSR6F), fuel filter (1140 120 1000), oil pump (1140 640 3201).
STIHL Limited Warranty: 1 year for homeowner use, 90 days for commercial use. Proof of purchase required. For technical support, contact an authorized STIHL dealer or visit www.stihlusa.com. This manual is for use by trained technicians only.