STIHL 028 WB Repair Manual

The STIHL 028 WB is a professional-grade chainsaw featuring a powerful engine, anti-vibration system, and advanced safety features. This repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair procedures. Below are key sections covering safety precautions, technical specifications, disassembly/assembly, fuel system, ignition system, carburetor adjustment, chain and bar maintenance, and common troubleshooting.

Safety Precautions

Always wear appropriate PPE: safety glasses, gloves, hearing protection, and chainsaw chaps. Ensure the chainsaw is completely cool before starting any repair work. Disconnect the spark plug wire to prevent accidental starting. Work in a well-ventilated area when handling fuel or cleaning parts.

Technical Specifications

• Engine Type: 2-stroke, single cylinder
• Displacement: 51.7 cc
• Power Output: 3.2 kW (4.3 hp)
• Fuel Capacity: 0.55 liters
• Oil Capacity: 0.26 liters
• Chain Pitch: 3/8" or .325"
• Bar Length: 16" to 20" (standard)
• Weight: 6.2 kg (without bar and chain)
• Ignition System: Electronic, breakerless
• Carburetor: Bing or Zama diaphragm type

Tools Required

Standard metric wrench set (8mm-17mm), Torx T27 screwdriver, spark plug wrench, piston stop tool, flywheel puller, compression tester, feeler gauges, carburetor adjustment tool, chain sharpening file.

NOTE: Use genuine STIHL tools for best results and to avoid damage to components.

Engine Disassembly

1. Remove top cover and air filter assembly.
2. Remove spark plug and install piston stop.
3. Remove clutch assembly using clutch removal tool.
4. Remove flywheel using puller tool.
5. Separate crankcase halves after removing all screws.
6. Extract crankshaft, connecting rod, and piston assembly.

WARNING! Mark all parts and fasteners for correct reassembly. Do not force components.

Fuel System Repair

Common issues: fuel leaks, poor running, hard starting.

1. Drain fuel tank completely.
2. Remove fuel lines and inspect for cracks.
3. Clean fuel filter inside tank.
4. Check fuel pump diaphragm for tears.
5. Inspect carburetor gaskets and seals.
6. Replace any worn or damaged components.

Tip: Use ethanol-free fuel to prevent carburetor varnish buildup.

Ignition System

Electronic ignition module testing:

1. Check spark plug gap (0.5mm).
2. Test ignition coil resistance: primary 0.5-1.5Ω, secondary 8-15kΩ.
3. Inspect flywheel magnets for damage.
4. Check stop switch continuity.
5. Replace module if no spark present.

CAUTION! Never crank engine with spark plug disconnected and grounded to cylinder - can damage ignition module.

Carburetor Adjustment

Standard settings (Bing carburetor):

• L (low speed): 1 turn open
• H (high speed): 1 turn open
• LA (idle): 1 turn open

Adjustment procedure:

1. Start with factory settings.
2. Warm up engine fully.
3. Adjust L screw for smooth idle.
4. Adjust H screw for maximum RPM (13,500-14,500).
5. Fine-tune LA for smooth acceleration.

Chain & Bar Maintenance

Anti-Vibration System

The STIHL 028 WB features rubber AV mounts to reduce operator fatigue.

1. Inspect rubber mounts for cracking or deterioration.
2. Check mounting bolts for proper torque (8-10 Nm).
3. Replace entire AV set if any mount is damaged.
4. Ensure all vibration dampeners are properly seated.

NOTE: Worn AV mounts can cause excessive vibration and handlebar fatigue.

Reassembly Guidelines

1. Clean all parts in solvent before reassembly.
2. Use new gaskets and seals throughout.
3. Apply two-stroke oil to piston and cylinder during assembly.
4. Torque crankcase screws in crisscross pattern (10-12 Nm).
5. Set ignition timing with feeler gauge (0.3mm air gap).
6. Adjust clutch spring tension properly.

WARNING! Do not overtighten fasteners - use torque wrench where specified.

Troubleshooting

Technical Support: Contact STIHL authorized service center for complex repairs.

Parts: Use only genuine STIHL replacement parts.