Husqvarna Chainsaw 340 Service Manual

The Husqvarna Chainsaw 340 is a professional-grade chainsaw designed for demanding cutting tasks. This service manual provides detailed instructions for maintenance, troubleshooting, and repair. It covers the 40.9cc, 2.0 HP engine, chain brake system, automatic oiler, anti-vibration system, air filtration, carburetor adjustment, ignition system, fuel system, and all critical safety procedures. Below are key sections for safety, specifications, maintenance procedures, troubleshooting, and parts identification.

1. Safety Information 2. Specifications 3. Maintenance Schedule 4. Engine Service 5. Chain & Bar Maintenance 6. Fuel System 7. Ignition System 8. Carburetor Adjustment 9. Troubleshooting 10. Parts Diagrams 11. Torque Specifications

Safety Information

Critical safety warnings and personal protective equipment (PPE) requirements.

Hazard	Precaution
Kickback	Always use reduced-kickback bar and chain; grip handle firmly; do not cut with tip.
Chain Brake	Test before each use; ensure it engages properly.
Fuel Handling	Use clean, fresh fuel mix (50:1); no smoking; refuel in well-ventilated area.
PPE	Wear chainsaw chaps, gloves, eye protection, hearing protection, helmet with face shield.
Working Area	Clear area of obstacles; ensure secure footing; keep bystanders away.
Hot Surfaces	Avoid contact with muffler and cylinder during/after operation.
Chain Tension	Adjust when cold; chain should snap back when pulled from bar.
Transport	Engage chain brake; use scabbard; carry with bar pointing rearward.
Maintenance	Disconnect spark plug wire before servicing.
Starting	Place on ground; hold front handle with left hand, pull starter with right.

Specifications

Engine: 40.9cc, 2-stroke, single cylinder.
Power Output: 2.0 HP (1.5 kW).
Fuel Tank Capacity: 0.47 US qt (0.45 L).
Oil Tank Capacity: 0.34 US qt (0.32 L).
Bar Length Options: 13", 15", 16", 18".
Chain Pitch: 3/8" Low Profile.
Chain Gauge: 0.050".
Ignition System: Electronic, air gap 0.3 mm (0.012").
Carburetor: Zama C1Q, adjustable H, L, T screws.
Idle Speed: 2700 RPM.
Max Power Speed: 9000 RPM.
Weight (Powerhead): 10.1 lbs (4.6 kg).

Maintenance Schedule

Follow this schedule to ensure optimal performance and longevity.

Before Each Use: Check chain tension, sharpness, and lubrication; inspect chain brake; check for loose fasteners.
Daily (or every 5 hours): Clean air filter; check fuel filter; clean cooling fins and cylinder cover.
Weekly (or every 25 hours): Clean spark arrestor screen; inspect spark plug; check anti-vibration elements.
Monthly (or every 100 hours): Replace fuel filter; clean carburetor; check clutch and sprocket.
Annually (or every 500 hours): Replace spark plug; decarbonize cylinder and muffler; inspect piston and cylinder.

WARNING! Always use genuine Husqvarna parts. Disconnect spark plug before any maintenance.

Engine Service

Procedures for cylinder, piston, crankshaft, and bearings.

Cylinder & Piston Inspection: Remove muffler; inspect cylinder walls for scoring; check piston ring gap (max 0.5 mm).
Crankshaft Seals: Check for leaks; replace if fuel/oil leaks are present at seals.
Bearings: Check for play or roughness; replace if damaged.
Compression Test: Should be at least 120 PSI (8.3 bar).
Muffler: Remove and clean spark arrestor screen monthly.

Note: Use a torque wrench for all engine fasteners. Refer to torque specifications section.

Chain & Bar Maintenance

Proper chain care ensures cutting efficiency and safety.

Chain Tension: Adjust when cold. Chain should snap back when pulled from bar groove.
Sharpening: Use round file (4.0 mm / 5/32") at 30° angle; maintain equal length on all cutters.
Depth Gauges: File down to 0.025" (0.65 mm) below cutter top with flat file and gauge.
Bar Maintenance: Clean bar groove; flip bar weekly for even wear; dress rails with flat file if burred.
Sprocket: Inspect for wear; replace if teeth are hooked or worn.
Oiler: Test oil flow by pointing bar at light surface and running at full throttle; adjust oiler screw if needed.

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

Fuel System

Fuel tank, lines, filter, and carburetor service.

Fuel Filter: Replace every 100 hours or if clogged.
Fuel Lines: Inspect for cracks; replace if brittle or leaking.
Fuel Cap: Ensure vent is clear.
Carburetor Diaphragms: Check for stiffness or tears; replace kit if necessary.
Fuel Mix: Use 50:1 ratio of unleaded gasoline (min 89 octane) to Husqvarna XP+ or equivalent 2-stroke oil.

WARNING! Never use fuel older than 30 days. Drain tank for long-term storage.

Ignition System

Spark plug, ignition module, and stop switch testing.

Component	Specification	Test Procedure
Spark Plug	NGK BPMR7A, gap 0.020" (0.5 mm)	Check for fouling, cracks; replace annually.
Ignition Module	Air gap 0.3 mm (0.012")	Use feeler gauge between flywheel and module.
Stop Switch	Continuity test	Should show continuity when pressed.
Flywheel	Key and taper inspection	Check for sheared key; clean taper with solvent.

Note: Weak spark may indicate faulty module or damaged flywheel magnets.

Carburetor Adjustment

Adjusting H (high), L (low), and T (idle) screws. Initial settings: L = 1 turn out, H = 1 turn out.

Warm Up: Run engine at half throttle for 5-10 minutes.
Idle Speed (T): Adjust so chain does not move at idle (approx 2700 RPM).
Low Speed (L): Turn in until engine runs rough, then out 1/4 turn for smooth acceleration.
High Speed (H): At full throttle, adjust for max RPM (9000 RPM), then rich slightly (turn out 1/8 turn).
Final Check: Chain must not move at idle; engine must accelerate smoothly.

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

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No spark, flooded, fuel issue	Check spark plug; dry plug; check fuel lines and filter.
Engine starts then dies	Clogged fuel filter, carb adjustment	Replace fuel filter; adjust L screw.
Poor performance	Dirty air filter, clogged spark arrestor	Clean air filter and spark arrestor screen.
Chain won't oil	Clogged oiler, empty tank, wrong oil	Clean oil passages; fill tank; use bar & chain oil.
Excessive vibration	Loose fasteners, worn AV mounts	Tighten all fasteners; replace anti-vibration mounts.
Chain rotates at idle	Idle speed too high	Adjust T screw counterclockwise.
Overheating	Dirty cooling fins, lean carb setting	Clean fins; check H screw setting.

Parts Diagrams

Reference diagrams for ordering genuine Husqvarna parts.

Diagram 1: Cylinder & Piston Assembly (Part # 503 87 65-01)
Diagram 2: Carburetor & Fuel System (Part # 545 00 41-02)
Diagram 3: Ignition System (Part # 537 23 40-01)
Diagram 4: Chain Brake & Clutch (Part # 501 87 84-03)
Diagram 5: Anti-Vibration System (Part # 501 84 25-01)
Diagram 6: Starter Assembly (Part # 537 21 62-01)

Note: Always use your model's serial number when ordering parts.

Torque Specifications

Critical fastener torque values (lbf-ft / Nm).

Fastener	Torque
Cylinder bolts (M6)	8.7 lbf-ft / 11.8 Nm
Clutch	36.2 lbf-ft / 49 Nm
Flywheel nut	43.5 lbf-ft / 59 Nm
Spark plug	18.1 lbf-ft / 24.5 Nm
Bar nuts	7.2 lbf-ft / 9.8 Nm
Muffler bolts	7.2 lbf-ft / 9.8 Nm
Handle bolts	10.1 lbf-ft / 13.7 Nm
Carburetor screws	2.2 lbf-ft / 3.0 Nm

WARNING! Overtightening can strip threads; undertightening can cause failure.