Husqvarna 50 Chainsaw Repair Manual

The Husqvarna 50 is a professional-grade chainsaw designed for demanding forestry and arborist work. This repair manual provides comprehensive instructions for maintenance, troubleshooting, and repair of the engine, fuel system, ignition, chain brake, clutch, guide bar, and cutting chain. Below are key sections covering safety, specifications, disassembly, component repair, assembly, and troubleshooting procedures.

1. Features at a Glance 2. Safety Precautions 3. Technical Specifications 4. Tools & Equipment Required 5. Engine Disassembly 6. Fuel System Repair 7. Ignition System Service 8. Chain Brake & Clutch Assembly 9. Guide Bar & Chain Maintenance 10. Reassembly & Adjustment 11. Troubleshooting Guide

Features at a Glance

Key components: 2-stroke engine, carburetor, ignition module, chain brake, centrifugal clutch, sprocket, guide bar, and cutting chain.

Feature	Description
Engine Type	2-stroke, single cylinder, air-cooled
Displacement	50.2 cm³ (3.06 cu in)
Power Output	2.5 kW (3.4 hp) at 9000 rpm
Fuel Tank Capacity	0.5 liters (0.13 US gal)
Oil Tank Capacity	0.25 liters (0.07 US gal)
Guide Bar Length	13-18 inches (33-45 cm)
Chain Pitch	3/8" or .325"
Ignition System	Electronic, capacitor discharge
Carburetor	Walbro or Zama diaphragm type
Weight (without bar/chain)	5.2 kg (11.5 lbs)

Safety Precautions

Always disconnect spark plug before any repair. Wear protective gloves and eyewear.

Work in a well-ventilated area away from open flames.
Drain fuel and chain oil before disassembly.
Use genuine Husqvarna replacement parts.
Secure chainsaw in a vise during repair.

WARNING! Fuel is highly flammable. Avoid sparks and heat sources. Chain can cause serious injury even when not running.

Technical Specifications

Engine Model: Husqvarna 50.
Bore x Stroke: 44 mm x 33 mm.
Compression Ratio: 8.5:1.
Spark Plug: Champion RCJ7Y or equivalent, gap 0.5 mm.
Idle Speed: 2700 rpm.
Maximum Power Speed: 9000 rpm.
Fuel Mix Ratio: 50:1 (2% oil) with Husqvarna XP+ oil.
Chain Oil: Husqvarna chain oil or SAE 30.
Clutch Engagement: 2800-3200 rpm.

Tools & Equipment Required

Basic mechanic's tool set plus specialty tools.

Required: Torx T27, T10; Socket set (8-13 mm); Feeler gauges; Compression tester; Carburetor adjustment tool; Chain breaker/riveter; Vise; Spark plug wrench.

Special Tools: Piston ring compressor; Flywheel puller (Husqvarna 502 50 86-01); Clutch removal tool (Husqvarna 502 51 41-02); Ignition tester.

Engine Disassembly

Remove external components first, then cylinder and crankshaft.

Remove top cover, air filter, and carburetor.
Remove muffler and spark plug.
Remove clutch and flywheel using specialty tools.
Remove cylinder head bolts, lift off cylinder.
Remove piston pin circlips, push out pin, remove piston.
Remove crankshaft seals and bearings if replacement needed.

CAUTION! Label all parts and fasteners. Do not force components.

Fuel System Repair

Carburetor overhaul and fuel line replacement.

Disconnect fuel lines, remove carburetor.
Disassemble carburetor, clean all parts in solvent.
Replace diaphragms, gaskets, and needle valve.
Check fuel filter in tank, replace if clogged.
Reassemble carburetor, adjust idle and high-speed screws to initial settings (L: 1 turn out, H: 1 turn out).

Tip: Use compressed air to clear carburetor passages.

Ignition System Service

Testing and replacing ignition module and spark plug.

Check spark plug condition and gap.
Test ignition coil with multimeter: primary 0.2-0.3 Ω, secondary 8-10 kΩ.
Replace ignition module if no spark or resistance out of spec.
Check stop switch and wiring for continuity.
Set air gap between flywheel and ignition module: 0.3 mm.

WARNING! Never crank engine with spark plug disconnected and grounded to cylinder—risk of ignition module damage.

Chain Brake & Clutch Assembly

Disassembly, inspection, and reassembly of safety and drive components.

Chain Brake: Remove handle cover, inspect band for wear, check spring tension, replace if band is cracked or worn thin.

Clutch: Remove with clutch tool, inspect shoes for wear, clean drum, replace if shoes are worn more than 0.5 mm. Lubricate bearing with high-temperature grease.

Guide Bar & Chain Maintenance

Sharpening, tensioning, and replacement procedures.

Remove bar and chain, clean bar groove and oil holes.
File cutters to correct angle (30° top plate, 10° side plate).
Check depth gauges, file to 0.65 mm below cutter.
Reinstall chain, adjust tension so chain snaps back when lifted from bar.
Lubricate sprocket nose bearing.

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

Reassembly & Adjustment

Reverse of disassembly with critical adjustments.

Install new crankshaft seals and gaskets.
Assemble piston with ring gaps aligned with pin.
Torque cylinder bolts to 10 Nm (7.4 ft-lb).
Set carburetor: Adjust idle screw for smooth idle at 2700 rpm, high-speed for maximum power without four-stroking.
Check chain brake function: Band should stop chain within 0.15 seconds.

Final Check: Compression > 120 psi, no fuel leaks, chain oil flow.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, fuel, or compression	Check spark, fuel delivery, compression >100 psi.
Engine runs poorly	Clogged carburetor, air leak	Clean carburetor, pressure test crankcase.
Chain doesn't turn	Worn clutch, broken sprocket	Inspect clutch shoes, replace sprocket.
Excessive vibration	Unbalanced flywheel, bent crankshaft	Check flywheel key, measure runout.
Chain oil not flowing	Clogged oil passages, faulty pump	Clean bar groove, check pump drive.

Service Note: For technical support, contact Husqvarna at 1-800-487-5962 or visit www.husqvarna.com.