Husqvarna 45 Chainsaw Repair Manual

The Husqvarna 45 is a professional-grade chainsaw known for its reliability and performance. This repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair of the Husqvarna 45 chainsaw, covering the engine, fuel system, ignition, chain brake, bar, chain, and other critical components. Below are key sections for safety, specifications, disassembly, repair procedures, and troubleshooting.

Safety Precautions

Before performing any repair, ensure the chainsaw is turned off, the spark plug wire is disconnected, and all moving parts have stopped. Wear appropriate personal protective equipment (PPE).

Specifications & Technical Data

Key technical specifications for the Husqvarna 45 chainsaw.

• Engine Type: 2-stroke, single cylinder, air-cooled.
• Displacement: 45.7 cc (2.79 cu in).
• Power Output: 2.2 kW (3.0 hp) at 9000 rpm.
• Fuel Tank Capacity: 0.47 L (0.12 US gal).
• Oil Tank Capacity: 0.26 L (0.07 US gal).
• Bar Length Options: 13" to 18" (33 cm to 45 cm).
• Chain Pitch: 3/8" or .325".
• Chain Gauge: 0.050" (1.3 mm).
• Ignition System: Electronic, SEM or equivalent.
• Carburetor: Walbro or Zama diaphragm type.
• Weight (powerhead): 4.7 kg (10.4 lbs).
• Spark Plug: Champion RCJ7Y or equivalent, gap 0.5 mm (0.020").

Tools & Equipment Required

Standard and specialized tools needed for repair.

1. Socket set (metric: 8mm, 10mm, 13mm).
2. Screwdrivers (flathead, Phillips #2, Torx T27).
3. Feeler gauge set (for spark plug and ignition gap).
4. Chain breaker and spinner tool.
5. Compression tester.
6. Multimeter (for ignition testing).
7. Carburetor adjustment tool (splined).
8. Piston stop tool or rope.
9. Flywheel puller (Husqvarna specific).
10. Clutch removal tool.

WARNING! Use correct tools to avoid damage to components. Do not substitute improper tools.

Engine System Repair

Procedures for cylinder, piston, crankshaft, and bearings.

1. Compression Test: Attach tester to spark plug hole; pull starter. Minimum 110 psi for proper operation.
2. Cylinder Inspection: Remove muffler; inspect cylinder walls for scoring. Light honing acceptable if minor.
3. Piston & Rings: Remove cylinder; check piston for cracks, ring grooves for wear. Replace if out of spec.
4. Crankshaft Seals: Check for leaks (air/fuel). Replace seals if worn or leaking.
5. Bearings: Check main bearings for smooth rotation; replace if rough or noisy.
6. Reassembly: Lubricate piston and rings with 2-stroke oil; ensure ring gaps are staggered.

CAUTION! Label parts during disassembly. Torque cylinder bolts to manufacturer specification (typically 10-12 Nm).

Fuel System Repair

Fuel tank, lines, filter, and pump repair.

Tip: Always use fresh, properly mixed 2-stroke fuel (50:1 ratio with Husqvarna XP+ oil or equivalent).

Ignition System Repair

Testing and replacing spark plug, coil, flywheel, and stop switch.

1. Spark Plug: Check electrode wear; adjust gap to 0.5 mm (0.020"). Replace if fouled or cracked.
2. Ignition Coil: Test with multimeter. Primary resistance: ~0.5-2.0 Ω; Secondary: ~5-15 kΩ. Replace if out of spec.
3. Air Gap: Set coil air gap to 0.2-0.3 mm (0.008-0.012") using feeler gauge.
4. Flywheel: Check for cracks or sheared key. Use puller for removal; do not hammer.
5. Stop Switch: Test continuity; switch should be open when off, closed when on.
6. Wiring Harness: Inspect for frayed or broken wires; repair with solder and heat shrink.

WARNING! Never crank engine with spark plug removed and wire grounded against cylinder—risk of coil damage.

Chain Brake & Clutch Repair

Servicing the chain brake band, clutch drum, springs, and centrifugal clutch.

Chain Brake: Inspect brake band for wear; replace if thickness below 1.5 mm. Check handle mechanism for smooth operation; lubricate pivot points.

Clutch: Remove with clutch tool. Inspect shoes for wear; replace if worn unevenly. Check clutch drum for grooves; replace or resurface if deep scoring present. Lubricate clutch bearing with high-temperature grease.

Springs: Replace clutch springs if stretched or broken. Ensure correct tension for proper engagement RPM.

CAUTION! The clutch assembly is under spring tension. Wear eye protection during disassembly.

Bar & Chain Maintenance

Guide bar maintenance, chain sharpening, and sprocket inspection.

1. Guide Bar: Clean bar groove; file edges if burred. Rotate bar regularly for even wear.
2. Chain Sharpening: Use round file matching chain pitch (typically 5.5 mm). Maintain 30° cutting angle; file all cutters evenly.
3. Depth Gauges: File depth gauges with flat file to 0.025" (0.65 mm) below cutter top.
4. Sprocket (rim or spur): Inspect for wear; replace if teeth are hooked or uneven.
5. Chain Tension: Adjust so chain snaps back when pulled from bar; not sagging from bottom.
6. Lubrication: Ensure oiler port is clear; use bar and chain oil, not waste oil.

WARNING! Always wear gloves when handling chain. A sharp chain is safer than a dull one.

Carburetor Adjustment

Setting idle, low-speed (L), and high-speed (H) jets.

1. Start with engine warm.
2. Turn L screw for smoothest acceleration from idle.
3. Turn H screw for maximum RPM (do not exceed 12,500 rpm).
4. Adjust T screw so chain does not move at idle.
5. Fine-tune: In cut, adjust for optimal power without bogging or leaning out (4-stroking slightly at full throttle in air is acceptable).

CAUTION! Over-leaning (turning screws in too far) can cause engine damage from overheating.

Reassembly & Final Checks

Steps to reassemble chainsaw and perform operational tests.

1. Install cylinder/piston assembly with new gasket.
2. Mount carburetor with new gaskets and insulator block.
3. Install flywheel and coil, setting proper air gap.
4. Assemble clutch and chain brake components.
5. Fit guide bar and chain; adjust tension.
6. Fill with fresh fuel and bar oil.
7. Final Checks: Verify all fasteners are tight. Check for fuel/oil leaks. Start engine and test throttle response, chain brake engagement, and oiler function.

Tip: Keep work area clean and organized to avoid losing small parts during reassembly.

Troubleshooting Guide

Common problems, causes, and solutions.

Reset: For electronic ignition modules, disconnect spark plug wire for 30 seconds to reset.

Service: For genuine Husqvarna parts and technical support, contact authorized dealer or visit www.husqvarna.com.