Stihl 038 Chainsaw Repair Manual

The Stihl 038 is a professional-grade chainsaw known for its durability and power. This repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair of the Stihl 038 series, including the 038 AV, 038 AV Super, and 038 Magnum models. It covers engine systems, fuel system, ignition, chain brake, lubrication, and electrical components. Below are key sections for safety, specifications, maintenance procedures, troubleshooting, and parts diagrams.

Safety Precautions

Always prioritize safety when performing repairs. Wear appropriate personal protective equipment (PPE).

Specifications & Identification

Identify your model via serial number plate on rear handle.

• Engine Type: Single-cylinder, two-stroke, air-cooled.
• Displacement: 61.5 cc (038), 72.2 cc (038 Super/Magnum).
• Power Output: 3.4 kW (4.6 hp) to 4.4 kW (5.9 hp) depending on model.
• Fuel/Oil Mix: 50:1 (Stihl HP Ultra or equivalent).
• Ignition: Electronic, breakerless.
• Bar Length Range: 16" to 25" (40 cm to 63 cm).
• Chain Pitch: 3/8" or .404" (varies by model).
• Weight (powerhead): 6.2 kg to 6.8 kg (13.7 lbs to 15 lbs).

WARNING! Use only Stihl-approved replacement parts to maintain performance and safety.

Routine Maintenance

Regular maintenance ensures longevity and safe operation.

1. Daily/Pre-Use: Check chain tension, sharpness, and lubrication. Inspect for loose fasteners.
2. Air Filter: Clean weekly (more often in dusty conditions). Replace if damaged.
3. Spark Plug: Clean and regap (0.5 mm / 0.020") every 50 hours. Replace annually.
4. Fuel Filter: Replace every 100 hours or if clogged.
5. Chain Sprocket: Inspect for wear; replace if teeth are hooked or worn.
6. Bar: Clean groove and oil holes; flip weekly for even wear.

CAUTION! Allow engine to cool completely before performing maintenance.

Engine Repair

Cylinder, piston, crankshaft, and bearings.

1. Compression Test: Should read 120-150 psi. Low compression indicates worn piston/rings.
2. Cylinder Inspection: Remove muffler to inspect cylinder walls for scoring.
3. Piston Replacement: Remove cylinder head; replace piston and rings as a set.
4. Crankshaft Seals: Replace if leaking (causes air leaks and lean run condition).
5. Bearings: Check for play; replace if rough or noisy.
6. Decompression Valve: Clean and test for proper sealing.

Note: Engine work requires special tools (puller, flywheel holder).

Fuel System

Carburetor, fuel lines, tank vent, and filter.

Tip: Use pressure/vacuum tester to check carburetor and intake for leaks.

Ignition System

Spark plug, ignition module (coil), flywheel, and stop switch.

1. Spark Test: Remove plug, ground to cylinder, pull starter. Look for strong blue spark.
2. Ignition Module: Test resistance (primary 0.2-0.4 Ω, secondary 8-12 kΩ). Replace if out of spec.
3. Flywheel: Check for cracks; ensure key is intact and woodruff keyway not sheared.
4. Air Gap: Set between flywheel magnets and coil legs (0.3 mm / 0.012").
5. Stop Switch: Test continuity; wire should break circuit when pressed.

WARNING! Never pull starter with spark plug disconnected and ungrounded.

Chain & Bar Maintenance

Proper chain care is critical for performance and safety.

1. Sharpening: Use correct round file size (typically 5.5 mm). Maintain 30° cutting angle.
2. Depth Gauges: File down to 0.65 mm (0.025") below cutter top.
3. Tension: Adjust so chain snaps back when pulled from bar.
4. Bar Rail Wear: Dress rails with flat file if uneven.
5. Sprocket Wear: Replace drive sprocket if worn (often with new chain).

CAUTION! Always wear cut-resistant gloves when handling chain.

Lubrication System

Oil pump, tank, and delivery lines.

• Oil Flow Test: Run saw at high RPM pointed at light surface; should see oil sling.
• Pump Adjustment: Screw on bottom of saw controls flow. Turn clockwise to increase.
• Oil Lines: Check for cracks or disconnections at pump and bar pad.
• Oil Filter: Clean screen in oil tank.
• Pump Worm Gear: Inspect for wear on drive gear.

Note: Use only Stihl chain oil or equivalent for proper adhesion.

Electrical System

Starter, alternator (for electronic ignition), and wiring.

1. Starter Rope: Replace if frayed. Rewind spring if necessary.
2. Rewind Spring: Lubricate lightly with grease during reassembly.
3. Wiring Harness:Inspect for chafing or breaks, especially near handles.