Husqvarna 445 Chainsaw Service Manual

The Husqvarna 445 is a professional-grade chainsaw featuring a 45.7cc X-Torq engine for reduced emissions and fuel consumption, an air injection system for cleaner air filters, a combined choke/stop control, inertia-activated chain brake, low vibration system, and Smart Start for easier starting. This manual covers essential safety, maintenance, troubleshooting, and repair procedures to ensure optimal performance and operator safety.

1. Safety Precautions 2. Specifications & Features 3. Component Identification 4. Maintenance Schedule 5. Fuel & Lubrication System 6. Engine Service 7. Chain & Bar Maintenance 8. Ignition System 9. Carburetor Adjustment 10. Troubleshooting Guide 11. Parts List & Diagrams

Safety Precautions

Always wear appropriate PPE: helmet, eye protection, hearing protection, gloves, chainsaw chaps, and sturdy boots. Never operate alone. Keep bystanders at a safe distance.

Hazard	Preventive Action
Kickback	Hold saw firmly with both hands; use low-kickback chain; avoid tip contact.
Fuel Handling	Refuel in well-ventilated area with engine off and cool; use approved fuel mix.
Chain Brake	Test before each use; ensure inertia function is operational.
Hot Surfaces	Allow engine to cool before maintenance; avoid muffler contact.
Falling Debris	Be aware of overhead hazards; clear work area.

Specifications & Features

Engine: 45.7cc X-Torq 2-stroke engine.
Power Output: 2.4 kW (3.2 hp).
Fuel Capacity: 0.5 liters (16.9 fl. oz).
Oil Tank Capacity: 0.25 liters (8.5 fl. oz).
Bar Length Options: 15", 16", 18".
Chain Pitch/Gauge: 3/8" LP, .050".
Weight (Powerhead): 4.9 kg (10.8 lbs).
Ignition System: Electronic, adjustable.
Vibration Damping: LowVib system with dampers.
Starting System: Smart Start with combined choke/stop control.

Component Identification

Key components: Front hand guard with chain brake, Throttle trigger lockout, Throttle trigger, Choke/Stop control, Air filter cover, Fuel tank cap, Oil tank cap, Muffler, Spark plug, Chain tensioner, Guide bar, Saw chain.

WARNING! Familiarize yourself with all controls before operation.

Maintenance Schedule

Daily/Before Use: Check chain tension, sharpness, and lubrication; inspect for loose parts; test chain brake; clean air filter.
Weekly/10 Hours: Clean cooling fins; check spark plug condition; clean fuel filter; inspect guide bar for wear.
Monthly/50 Hours: Clean carburetor air intake; replace fuel filter; check fuel lines for cracks; clean spark arrestor screen.
Annually/100 Hours: Replace spark plug; clean cylinder and exhaust port; check clutch and sprocket; replace air filter.

CAUTION! Use only genuine Husqvarna parts for replacement.

Fuel & Lubrication System

Fuel Mix: Use 50:1 mixture of unleaded gasoline (min 90 octane) and Husqvarna 2-stroke oil. Do not use automotive oil.

Fuel System Cleaning: Remove tank, clean with solvent, replace fuel filter and lines if cracked.
Oil Pump Adjustment: Located under clutch cover; adjust screw to increase/decrease bar oil flow.
Oil Line Inspection: Check for leaks or blockages; replace if damaged.

Tip: Always shake fuel mix before refueling.

Engine Service

Cylinder & Piston: Inspect for scoring; replace if wear exceeds limits. Crankshaft Seals: Check for leaks; replace if engine runs lean. Muffler: Clean regularly to prevent carbon buildup.

Compression Test: Should read 120-150 psi. Low compression indicates worn piston rings or cylinder.

Chain & Bar Maintenance

Chain Sharpening: Use round file matching chain pitch; maintain correct filing angle (30°).
Bar Maintenance: Clean bar groove; flip bar regularly for even wear; check for straightness.
Chain Tension: Adjust when cool; proper tension allows chain to snap back when lifted from bar.
Sprocket Inspection: Replace if worn; ensure clutch drum rotates freely.

WARNING! Always wear gloves when handling chain.

Ignition System

Spark Plug: NGK BPMR7A, gap 0.5 mm. Check electrode condition; replace if fouled or worn. Ignition Module: Test with multimeter; resistance values specified in wiring diagram. Stop Switch: Ensure circuit breaks when engaged.

Carburetor Adjustment

Adjustment Screws: L (low speed), H (high speed), T (idle). Initial settings: L=1 turn open, H=1 turn open. Fine-tune at operating temperature.

Idle Speed: Adjust T screw so chain does not move at idle.
Acceleration: Adjust L for smooth transition from idle to high speed.
High Speed: Adjust H for maximum RPM (13,500-14,500); use tachometer.

CAUTION! Over-leaning can cause engine damage.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, flooded, fuel issue	Check spark plug, air filter; use correct starting procedure; ensure fuel mix fresh.
Engine runs poorly	Dirty air/fuel filter, carb adjustment	Clean/replace filters; adjust carburetor; check fuel lines.
Chain doesn't turn	Clutch worn, sprocket damaged	Inspect clutch springs and shoes; replace sprocket if worn.
Excessive vibration	Loose components, unbalanced chain	Tighten all bolts; balance chain; check anti-vibration mounts.
Chain oil not flowing	Clogged oil passages, pump failure	Clean oil holes in bar; check pump operation; replace if faulty.

Parts List & Diagrams

Refer to official Husqvarna parts catalog for exploded views and part numbers. Common replacement parts: Air filter (503 92 76-01), Fuel filter (501 87 65-01), Spark plug (NGK BPMR7A), Chain brake band (537 00 39-01), Clutch assembly (537 01 18-01).

Service Support: Contact authorized Husqvarna dealer or visit www.husqvarna.com. Technical support: 1-800-487-5962.