STIHL 026 Service Repair Manual

The STIHL 026 is a professional-grade chainsaw known for its reliability and power. This service and repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair of the STIHL 026 chainsaw. It covers engine systems, fuel system, ignition system, chain brake, guide bar, cutting chain, and all other major components. Below are key sections for safety, specifications, maintenance procedures, disassembly/assembly, troubleshooting, and parts identification.

Safety Precautions & Warnings

Before performing any service, read all safety instructions. Always wear appropriate personal protective equipment (PPE).

Hazard	Precaution
Fuel Fire/Explosion	Work in well-ventilated area away from sparks or flames. Drain fuel before service.
Sharp Chain Injury	Always wear cut-resistant gloves. Ensure chain brake is engaged when not cutting.
Hot Surfaces	Allow engine and muffler to cool completely before handling.
Spring-Loaded Components	Use proper tools; be aware of stored energy in brake springs and starter springs.
Electrical Shock	Disconnect spark plug wire before working on ignition system.

WARNING! Failure to follow safety procedures can result in serious injury or death. This manual is for qualified technicians only.

Specifications & Identification

• Model: STIHL 026
• Engine Type: Single-cylinder, two-stroke, air-cooled
• Displacement: 49.4 cc (3.01 cu in)
• Power Output: 2.6 kW (3.5 hp) @ 13,000 rpm
• Fuel/Oil Ratio: 50:1 (STIHL HP Ultra or equivalent)
• Ignition System: Electronic, breakerless
• Spark Plug: Bosch WSR6F or equivalent, gap 0.5 mm (0.020 in)
• Idle Speed: 2,800 rpm
• Max. Engine Speed: 13,500 rpm (with bar and chain)
• Chain Pitch: 3/8" PM or .325"
• Bar Length Range: 16" to 20" (40 cm to 50 cm)
• Weight (powerhead): 5.2 kg (11.5 lbs) dry

Serial Number Location: Stamped on crankcase near rear handle.

Regular Maintenance Schedule

Follow this schedule to ensure optimal performance and longevity.

1. Before Each Use: Check chain tension, sharpness, and lubrication. Inspect for loose fasteners or damage.
2. Every 10 Hours: Clean air filter. Check spark plug condition and gap.
3. Every 20 Hours: Clean spark arrestor screen in muffler. Check fuel filter.
4. Every 50 Hours: Replace fuel filter. Clean cooling fins. Check carburetor adjustment.
5. Every 100 Hours: Replace spark plug. Clean cylinder exhaust port. Inspect clutch and sprocket.
6. Annually: Replace air filter. Check all rubber mounts and antivibration elements.

CAUTION! Use only genuine STIHL or approved replacement parts.

Fuel System Service

Components: Fuel tank, cap, lines, filter, carburetor (Walbro or Zama).

1. Fuel Tank Cleaning: Drain fuel. Remove tank. Flush with clean fuel. Inspect for cracks.
2. Fuel Line Replacement: Remove old lines. Cut new lines to exact length. Ensure secure connections to tank, filter, and carburetor.
3. Fuel Filter Replacement: Use hook tool to extract filter from tank. Soak new filter in fuel before installation.
4. Carburetor Removal: Disconnect fuel lines and throttle linkage. Remove mounting nuts.

Tip: Always pressure test fuel system for leaks after reassembly.

Ignition System Service

Components: Flywheel, ignition module (coil), spark plug, stop switch, wiring.

1. Spark Test: Remove spark plug, reconnect wire, ground plug against cylinder. Pull starter; look for strong blue spark.
2. Air Gap Adjustment: Set gap between ignition module legs and flywheel magnets to 0.3 mm (0.012 in).
3. Module Replacement: Remove flywheel. Note wiring routing. Install new module and set air gap.
4. Stop Switch Test: Use multimeter to check for continuity when switch is pressed.

WARNING! Never crank engine with spark plug disconnected and wire ungrounded.

Engine Service & Overhaul

Major procedures: Cylinder and piston inspection, crankshaft bearing replacement, crankcase splitting.

1. Compression Test: Should be a minimum of 120 psi. Low compression indicates worn piston/rings or cylinder.
2. Cylinder Inspection: Remove muffler to inspect piston and cylinder through exhaust port. Look for scoring or aluminum transfer.
3. Piston Replacement: Remove cylinder. Install new piston with arrow facing exhaust port. Use ring compressor.
4. Crankcase Sealing: Use STIHL Dirko or equivalent sealant on case halves. Torque screws in crisscross pattern.

CAUTION! Label all parts during disassembly. Replace all gaskets and seals during reassembly.

Chain Brake System

Components: Brake band, lever, spring, activation mechanism.

1. Band Inspection: Check for wear, glazing, or cracks. Minimum thickness: 1.5 mm.
2. Band Replacement: Remove clutch drum and sprocket. Slide off old band, install new one.
3. Spring Tension: Ensure return spring is properly seated and provides positive brake release.
4. Function Test: With saw off, activate brake by hand; band should fully engage clutch drum. Release should be smooth.

WARNING! A malfunctioning chain brake will not stop the chain in a kickback event. Test thoroughly.

Guide Bar & Cutting Chain

Maintenance: Cleaning, dressing, replacement.

1. Bar Cleaning: Remove bar. Clean oil passages with wire. File out burrs on rails.
2. Bar Dressing: Use flat file to true up rails. Ensure groove depth is consistent.
3. Chain Sharpening: Use correct round file size (typically 4.0 mm or 5/32"). Maintain correct filing angle (30°).
4. Depth Gauge Setting: Use depth gauge tool and flat file to set rakers 0.025" below cutter top plate.

Tip: Rotate bar regularly to promote even wear. Always use sharp chain for safety and performance.

Carburetor Adjustment

Adjustment screws: L (low speed), H (high speed), LA (idle speed).

1. Initial Settings: Turn L and H screws gently clockwise until seated, then back out 1 turn each.
2. Final Adjustment (Warm Engine):
   • Adjust L screw for fastest idle, then turn out 1/4 turn.
   • Adjust H screw for maximum RPM, then turn in (richer) until RPM drops slightly (prevents lean seizure).
   • Set idle speed with LA screw so chain just stops moving, and engine runs smoothly.
3. Acceleration Test: Throttle should respond instantly without hesitation or stalling.

CAUTION! A lean H setting will cause engine damage. Use tachometer for precise adjustment.

Electrical System

Testing: Stop switch, wiring harness, ignition module.

Component	Test Procedure	Specification
Stop Switch	Continuity test between black wire and ground	Continuity when pressed; open when released
Wiring Harness	Visual inspection & continuity check	No cracks, breaks, or shorts to ground
Ignition Module	Primary/Secondary resistance (if applicable)	Refer to module-specific specs

Note: Most STIHL modules are non-serviceable; replace if faulty.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, fuel issue	Check spark, plug condition. Dry plug. Check fuel lines, filter, carburetor.
Engine starts then dies	Fuel starvation, air leak	Check fuel vent, filter, carburetor diaphragms. Pressure test crankcase.
Lacks power/overheats	Clogged air filter, muffler screen, lean carb setting	Clean filter and spark arrestor. Check H screw setting. Inspect piston for scoring.
Chain does not oil	Clogged oil passages, faulty pump, wrong oil	Clean bar and oil ports. Test pump output. Use STIHL chain oil.
Excessive vibration	Unbalanced chain, loose components, worn AV mounts	Sharpen chain properly. Tighten all fasteners. Replace antivibration elements.
Clutch slips/does not engage	Worn clutch shoes, weak springs, greasy drum	Replace clutch assembly. Clean clutch drum with solvent.

Torque Specifications

Use a calibrated torque wrench. Values in Nm (ft-lbs).

• Cylinder nuts: 20 Nm (14.8 ft-lbs)
• Spark plug: 25 Nm (18.4 ft-lbs)
• Clutch: 40 Nm (29.5 ft-lbs) - LEFT-HAND THREAD
• Flywheel nut: 40 Nm (29.5 ft-lbs)
• Crankcase screws: 10 Nm (7.4 ft-lbs)
• Guide bar nuts: 12 Nm (8.9 ft-lbs)
• Muffler bolts: 10 Nm (7.4 ft-lbs)

Note: Apply thread locker (Loctite 243) to clutch and flywheel threads.

Parts Diagrams & Lists

Refer to official STIHL parts catalog for exploded views and part numbers. Major groups:

1. Crankcase Assembly
2. Cylinder & Piston Group
3. Carburetor & Air Filter
4. Ignition System
5. Clutch & Sprocket
6. Chain Brake Assembly
7. Fuel Tank & Handle
8. Guide Bar & Chain
9. External Covers & Hardware

Ordering Parts: Always provide model number (026) and serial number.

Support: For technical assistance or to order parts, contact an authorized STIHL servicing dealer or visit www.stihlusa.com.