Husqvarna 450 Chainsaw Parts Manual

The Husqvarna 450 is a professional-grade chainsaw featuring a 50.2cc X-Torq engine for reduced emissions and fuel consumption, Smart Start for easy starting, Air Injection centrifugal air cleaning system, LowVib anti-vibration system, inertia-activated chain brake, combined choke/stop control, and quick-release air filter. This parts manual provides detailed diagrams, part numbers, and ordering information for maintenance and repair. Below are key sections for safety, specifications, parts diagrams, assembly instructions, maintenance, and troubleshooting.

Features at a Glance

Key components: X-Torq engine, Air Injection system, Smart Start, LowVib, inertia chain brake, combined choke/stop control, quick-release air filter, side-mounted chain tensioner.

Safety Information

Always wear protective equipment: helmet, goggles, hearing protection, gloves, chainsaw chaps, and steel-toed boots.

1. Pre-Operation Check: Inspect chain tension, sharpness, and lubrication; check all fasteners.
2. Starting: Place on flat ground, engage chain brake, follow starting procedure.
3. Operation: Maintain secure footing, keep bystanders away, avoid kickback zone.
4. Transport: Engage chain brake, use scabbard, secure in vehicle.

WARNING! Chainsaw kickback can cause serious injury. Always hold saw firmly with both hands. Never operate above shoulder height.

Specifications

• Engine Displacement: 50.2 cc (3.06 cu in)
• Power Output: 3.2 HP (2.4 kW)
• Fuel Tank Volume: 0.55 US qt (0.52 liter)
• Oil Tank Volume: 0.42 US qt (0.40 liter)
• Recommended Bar Length: 13" to 20" (33 cm to 50 cm)
• Chain Pitch: 3/8" or .325"
• Chain Gauge: 0.050" (1.3 mm)
• Weight (excl. cutting equipment): 10.8 lbs (4.9 kg)
• Sound Pressure Level: 106 dB(A)
• Vibration Levels: Front handle: 3.2 m/s², Rear handle: 4.5 m/s²

Parts Diagrams & Lists

Detailed exploded-view diagrams with corresponding part numbers for ordering.

Cylinder & Piston Assembly: Part # 537 01 74-01 (Cylinder), 537 01 74-02 (Piston), 537 01 74-03 (Piston Rings).

Crankshaft & Bearings: Part # 537 02 18-01 (Crankshaft), 537 02 18-02 (Main Bearings).

Carburetor Assembly: Part # 537 03 25-01 (Zama C1Q-S267), 537 03 25-02 (Diaphragm Kit).

Ignition System: Part # 537 04 12-01 (Ignition Module), 537 04 12-02 (Spark Plug NGK BPMR7A).

Fuel System: Part # 537 05 33-01 (Fuel Tank), 537 05 33-02 (Fuel Filter), 537 05 33-03 (Fuel Line).

Chain Brake/Clutch: Part # 537 06 41-01 (Clutch Drum), 537 06 41-02 (Chain Brake Band).

Bar & Chain: Part # 537 07 59-01 (Guide Bar 18"), 537 07 59-02 (Sprocket Nose), 537 07 59-03 (Chain 3/8" .050" 72DL).

Assembly Instructions

Assembling bar and chain, attaching handles, initial setup.

1. Mount Guide Bar: Place bar on studs, align chain with sprocket, install bar nuts finger-tight.
2. Install Chain: Position chain on bar with cutters facing forward, engage drive links in sprocket.
3. Tension Chain: Lift bar tip, tighten chain using side tensioner until snug against bar.
4. Final Tightening: Tighten bar nuts securely while holding bar tip up.
5. Handle Attachment: Ensure all vibration dampeners are in place before tightening handle bolts.

Tip: Always check chain tension when cold. A properly tensioned chain should snap back when pulled from the bar.

Maintenance Schedule

Daily/Before Use: Check chain tension/sharpness, fuel/oil levels, air filter, all fasteners.

Weekly/10 Hours: Clean air filter, check spark plug, clean cooling fins, inspect chain brake function.

Monthly/50 Hours: Replace fuel filter, clean spark arrestor, check carburetor adjustment, lubricate clutch bearing.

Seasonal/100 Hours: Replace spark plug, clean fuel tank, inspect fuel lines, check clutch springs.

Annual/300 Hours: Replace air filter, check cylinder compression, inspect piston through exhaust port.

Carburetor Adjustment

Factory settings: L screw - 1 turn out, H screw - 1 turn out, T screw - 1 turn out.

1. Warm up engine for 5 minutes before adjustment.
2. Set idle speed (T screw): Adjust until chain just stops moving, then 1/4 turn counterclockwise.
3. Set low speed (L screw): Turn for smoothest acceleration from idle.
4. Set high speed (H screw): Never exceed 13,500 RPM (use tachometer).
5. Final check: Chain must not move at idle; engine must accelerate smoothly.

CAUTION! Improper adjustment can cause engine damage. H screw affects maximum RPM - do not over-lean.

Chain & Bar Maintenance

Chain sharpening: Use 5/32" (4.0mm) round file at 30° angle, maintain depth gauge at 0.025" (0.65mm).

1. File each cutter evenly with equal strokes.
2. Check depth gauges after every 3-4 sharpenings.
3. Rotate bar regularly to ensure even wear.
4. Clean bar groove and oil holes daily.
5. File drive links if burred to prevent bar groove wear.

WARNING! Always wear gloves when handling chain. A sharp chain reduces kickback risk.

Fuel & Lubrication System

Fuel: Use 89 octane minimum gasoline mixed with 2-stroke oil at 50:1 ratio (Husqvarna XP+ or equivalent).

Bar Oil: Use quality chainsaw bar oil (viscosity appropriate for temperature).

1. Mix fuel in clean container, not in saw tank.
2. Shake fuel mixture thoroughly before refueling.
3. Clean fuel cap area before opening to prevent contamination.
4. Check oiler output: Run saw at full throttle over light surface; should throw oil line.
5. Adjust oiler if needed: Turn screw clockwise for more oil, counterclockwise for less.

CAUTION! Never use automotive motor oil or fuel older than 30 days. Stale fuel causes starting problems.

Ignition System

Spark Plug: NGK BPMR7A (gapped at 0.020" / 0.5mm).

Ignition Module: Solid-state electronic, air gap 0.010" (0.25mm).

Stop Switch: Test for continuity when pressed.

Troubleshooting: No spark - check plug, wire connection, stop switch, module ground, flywheel key.

Troubleshooting

Service: For genuine Husqvarna parts, contact authorized dealer or visit www.husqvarna.com. Technical support: 1-800-487-5962.