Stihl 026 Repair Manual

The Stihl 026 is a professional-grade chainsaw known for its reliability and performance in light to medium-duty forestry and cutting applications. This repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair of the Stihl 026 chainsaw, covering the engine, fuel system, ignition, chain brake, clutch, guide bar, and cutting chain. Below are key sections for safety, specifications, disassembly, component repair, reassembly, and troubleshooting.

Features at a Glance

Key components: Single-cylinder two-stroke engine, Electronic ignition (CDI), Decompression valve, Anti-vibration system, Chain brake, Automatic oiler, Manual oil pump, Quickstop inertia chain brake.

Feature	Description
Engine Displacement	49.4 cc (3.01 cu in)
Power Output	2.6 kW (3.5 hp)
Fuel Tank Capacity	0.55 L (18.6 fl oz)
Oil Tank Capacity	0.26 L (8.8 fl oz)
Guide Bar Lengths	Typically 16" to 20" (40 cm to 50 cm)
Ignition System	Electronic, capacitor discharge (CDI)
Weight (powerhead)	Approx. 5.2 kg (11.5 lbs)
Chain Pitch	3/8" PM or .325"
Chain Brake	Inertia-activated Quickstop
Anti-Vibration	Spring-mounted handles

Safety Precautions

Always prioritize safety when performing repairs. Chainsaws are dangerous tools.

1. Disconnect Spark Plug: Always remove the spark plug boot before starting any repair to prevent accidental starting.
2. Work in a Clean Area: Keep workspace organized to avoid losing small parts.
3. Use Proper Tools: Use Stihl special tools or equivalents where specified.
4. Handle Fuel Safely: Drain fuel tank before working on fuel system; work in well-ventilated area.
5. Wear PPE: Safety glasses and gloves are recommended during disassembly.

WARNING! Failure to follow safety procedures can result in serious injury or death. The chainsaw must be completely cool before beginning work.

Specifications

• Engine Type: Single-cylinder, two-stroke, air-cooled.
• Bore x Stroke: 44 mm x 32 mm.
• Compression Ratio: Approx. 8.5:1.
• Fuel Mix: 50:1 (Gasoline to high-quality 2-stroke oil).
• Carburetor: Walbro or Zama diaphragm carburetor.
• Spark Plug: Bosch WSR6F or equivalent, gap 0.5 mm (0.020").
• Idle Speed: 2,800 - 3,200 RPM.
• Maximum Power Speed: Approx. 12,500 RPM.
• Chain Oil: Use STIHL chain oil or equivalent.
• Torque Values: Cylinder bolts: 20 Nm (15 ft-lb); Clutch: 40 Nm (30 ft-lb).

Tools Required

Standard and special tools needed for repair.

• Torx screwdrivers (T27, T10)
• Socket set (8mm, 10mm, 13mm)
• Spark plug wrench
• Piston stop tool (Stihl 1129 893 4500)
• Clutch removal tool (Stihl 0000 893 4303)
• Flywheel puller (Stihl 1129 893 4503)
• Compression tester
• Vacuum/pressure tester for crankcase
• Feeler gauges
• Multimeter

Disassembly Procedure

Systematic teardown to access internal components.

1. External Cleaning: Remove dirt and debris from exterior.
2. Remove Top Covers: Remove rear handle cover and air filter cover.
3. Remove Air Filter & Carburetor: Disconnect fuel lines and throttle linkage.
4. Remove Muffler: Unbolt muffler to inspect piston through exhaust port.
5. Remove Starter Assembly: Remove recoil starter.
6. Remove Flywheel: Use flywheel puller after removing nut with piston stop.
7. Remove Cylinder: Unbolt cylinder head; may require gentle tapping if stuck.
8. Remove Clutch & Sprocket: Use clutch tool to remove left-hand thread clutch.
9. Separate Crankcase Halves: Requires special care to avoid damage to bearings and seals.

Tip: Take photos during disassembly and organize parts in labeled containers.

Engine Repair

Focus on piston, cylinder, crankshaft, and bearings.

1. Piston Inspection: Check for scoring, ring wear, and pin bearing play. Replace if damaged.
2. Cylinder Inspection: Inspect for scoring or plating damage. Light honing possible if Nikasil plating is intact.
3. Crankshaft & Bearings: Check for play and smooth rotation. Replace bearings if rough or noisy.
4. Crankcase Seals: Critical for engine vacuum/pressure. Replace if leak is suspected (test with pressure/vacuum).
5. Reed Valve: Check for cracks or improper sealing on the intake block.
6. Decompression Valve: Test for proper opening and sealing.

WARNING! Use genuine Stihl or OEM parts for critical engine components to ensure proper fit and performance.

Fuel System Service

Carburetor repair and fuel line replacement.

1. Drain Fuel Tank: Remove fuel and clean tank.
2. Replace Fuel Lines & Filter: Cracked or stiff lines are common failure points.
3. Carburetor Rebuild: Disassemble carburetor, clean all jets and passages, replace diaphragms, gaskets, and needle valve. Adjust H and L screws to base settings: L - 1 turn out, H - 1 turn out.
4. Fuel Pump Diaphragm: Check for cracks or stiffness.
5. Tank Vent: Ensure the tank vent is clear.

CAUTION! Use only ethanol-resistant fuel lines and diaphragms if using ethanol-blended fuel.

Ignition System

Testing and replacement of ignition components.

• Spark Test: Remove spark plug, ground it against cylinder, pull starter. Look for strong blue spark.
• Coil Air Gap: Set between 0.2 mm - 0.4 mm (0.008" - 0.016") using a feeler gauge.
• Coil Resistance: Primary winding: ~0.5 - 2.0 Ω; Secondary: ~5k - 15k Ω (check service manual for exact specs).
• Switch & Wiring: Check stop switch for continuity when off/open when on. Inspect wires for breaks.
• Flywheel Magnets: Ensure they are clean and undamaged.

Chain Brake & Clutch

Service of the safety and drive components.

1. Chain Brake Band: Inspect for wear or glazing. Replace if thickness is below specification.
2. Brake Handle Mechanism: Clean and lubricate pivot points. Ensure spring returns handle.
3. Clutch Drum & Sprocket: Check for wear on sprocket teeth and drum bearing. Replace if worn.
4. Clutch Shoes & Springs: Inspect shoes for wear and springs for fatigue or breakage.
5. Needle Bearing: Lubricate clutch drum needle bearing with high-temperature grease.

Guide Bar & Chain

Maintenance of cutting components.

1. Bar Inspection: Check for straightness, rail wear, and groove cleanliness. Dress rails with a flat file if uneven.
2. Chain Sharpening: Maintain correct filing angle (typically 30°) and depth gauge height.
3. Oil Flow Check: Run saw at high idle without chain; oil should fling from tip of bar.
4. Oil Pump Adjustment: Adjust screw near oil pump for more/less output.
5. Sprocket Nose Bar: Grease sprocket nose regularly if equipped.

Reassembly Guide

Reverse of disassembly with critical notes.

1. Crankcase Sealing: Use a thin, even layer of high-quality gasket sealant (e.g., Dirko) on crankcase halves. Torque bolts in a criss-cross pattern to specification.
2. Crankshaft Seals: Install new seals flush, lubricating lips with grease.
3. Piston Installation: Ensure ring ends are seated over locating pins. Use a piston ring compressor.
4. Cylinder Installation: Lubricate piston and cylinder wall with 2-stroke oil before sliding cylinder on.
5. Flywheel Installation: Torque nut to 40 Nm (30 ft-lb). Ensure woodruff key is properly seated.
6. Carburetor Adjustment: After reassembly, start saw and fine-tune L and H screws for smooth idle and acceleration. Finalize with a tachometer: Idle ~2800 RPM, Max ~12500 RPM.

CAUTION! Do not over-torque fasteners, especially in magnesium crankcase.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, fuel, or compression	Check spark, fuel delivery, and compression (should be >110 psi).
Engine starts then dies	Clogged fuel filter, tank vent, carb issues	Replace fuel filter, clear vent, rebuild carburetor.
Lacks power/overheats	Air leak, clogged muffler, carb adjustment	Pressure test crankcase, clean spark arrestor, adjust carb.
Chain won't turn	Clutch worn, brake engaged, sprocket worn	Inspect clutch shoes/springs, disengage brake, replace sprocket.
Excessive vibration	Damaged anti-vibration mounts, unbalanced flywheel	Replace AV mounts, check flywheel for damage.
Oil not pumping	Clogged oil passages, faulty pump, wrong oil	Clean oil channels, inspect/replace pump, use correct oil.
Chain brake doesn't engage	Worn brake band, weak spring, dirty mechanism	Replace brake band/spring, clean and lubricate handle mechanism.

Final Check: After repair, run saw at idle and check for leaks, unusual noises, and proper chain brake function before putting into service.

Service & Parts: For genuine Stihl parts and technical support, contact an authorized Stihl dealer or visit www.stihlusa.com.