Husqvarna 142 Chainsaw Workshop Manual

The Husqvarna 142 is a lightweight, professional-grade chainsaw designed for demanding forestry and arborist work. This workshop manual provides comprehensive technical information for maintenance, repair, and overhaul procedures. It covers the 40.9cc 2-stroke engine, fuel system, ignition system, cutting equipment, safety features, and troubleshooting. Below are key sections for specifications, safety, disassembly, maintenance, and repair.

1. Specifications & Identification 2. Safety Precautions 3. General Maintenance 4. Engine System 5. Fuel System 6. Ignition System 7. Cutting Equipment 8. Clutch & Drive 9. Troubleshooting 10. Torque Specifications 11. Exploded Views & Parts List

Specifications & Identification

Key identification data and technical specifications for the Husqvarna 142 chainsaw.

Feature	Specification
Engine Type	2-stroke, single cylinder, air-cooled
Displacement	40.9 cc
Power Output	2.0 kW (2.7 hp)
Fuel Tank Volume	0.47 liter
Oil Tank Volume	0.26 liter
Recommended Bar Length	13" to 16" (33 cm to 40 cm)
Chain Pitch	3/8" LP or .325"
Idle Speed	2700 rpm
Max Power Speed	9000 rpm
Weight (Powerhead)	4.7 kg (10.4 lbs)
Ignition System	Electronic, SEM
Spark Plug	NGK BPMR7A (Champion RCJ7Y)

Safety Precautions

Critical safety warnings and procedures to follow before performing any work on the chainsaw.

Disconnect Spark Plug: Always remove the spark plug cap before starting any repair to prevent accidental starting.
Work in a Clean Area: Keep workspace clean and well-lit to avoid contamination and errors.
Use Proper Tools: Utilize Husqvarna special tools or equivalents as specified.
Handle Fuel Safely: Drain fuel tank before working on fuel system. Work in a ventilated area away from sparks or flames.
Wear PPE: Use safety glasses and gloves when handling sharp components like the chain and bar.

WARNING! Failure to follow safety procedures can result in serious injury or death. The chain can kick back even when the engine is off.

General Maintenance

Routine maintenance schedule and procedures to ensure optimal performance and longevity.

Daily/Before Use: Check chain tension, sharpness, and lubrication. Inspect for loose nuts and bolts.
Weekly/Every 10 Hours: Clean air filter. Check spark plug condition and gap (0.5 mm / 0.020"). Clean cooling fins and external surfaces.
Monthly/Every 20 Hours: Clean fuel filter. Check carburetor adjustment. Inspect clutch drum and sprocket for wear.
Annually/Every 100 Hours: Replace fuel filter and spark plug. Clean muffler spark arrestor screen. Check all rubber mounts and antivibration elements.

CAUTION! Use only Husqvarna-approved 2-stroke oil at a 50:1 mix ratio with fresh, unleaded gasoline (min 90 octane). Do not use automotive oil.

Engine System

Cylinder & Piston: Inspection for scoring, carbon buildup, and ring wear. Piston ring end gap limit: 0.8 mm.
Crankshaft & Bearings: Check for play and smooth rotation. Main bearing radial play limit: 0.05 mm.
Crankcase: Sealing check. Use gasket sealant (ThreeBond 1184 or equivalent) during reassembly.
Decompression Valve: Test operation. Clean or replace if leaking.
Muffler: Remove and clean carbon deposits. Inspect for cracks. Replace spark arrestor screen if clogged.

Fuel System

Components: Fuel tank, cap, lines, filter, and carburetor (Zama C1U or Walbro WT).

Carburetor Adjustment (Standard Settings): L (Low) screw: 1 turn open. H (High) screw: 1 turn open. T (Idle) screw: 1 turn open. Fine-tune at operating temperature.

Fuel Pump Diaphragm: Inspect for stiffness or cracks. Replace kit if faulty.

Fuel Line Replacement: Use ethanol-resistant line. Ensure proper routing to avoid kinks.

Ignition System

SEM electronic ignition module. No user-adjustable timing.

Spark Test: Remove spark plug, reconnect cap, ground plug against cylinder, pull starter. Look for strong blue spark.
Coil Air Gap: Set between 0.2 mm and 0.4 mm using a feeler gauge. Adjust by loosening coil mounting screws.
Stop Switch: Test for continuity when pressed. Replace if circuit does not open/close correctly.
Flywheel: Check key and keyway for shearing. Torque nut to 40-50 Nm (30-37 ft-lbs).

Tip: Weak or no spark is most commonly caused by a faulty spark plug, improper coil gap, or a failed ignition module.

Cutting Equipment

Guide bar, saw chain, drive sprocket, and chain brake system.

Bar Maintenance: Clean bar groove. File down burrs on rails. Rotate bar regularly for even wear.
Chain Sharpening: Maintain correct filing angle (30° for cutters, 80° for depth gauges). Keep all cutters equal length.
Sprocket Inspection: Replace spur sprocket every 2 chains or rim sprocket when visibly worn.
Chain Brake Function Test: With engine off, engage brake by hand; it should lock chain. Check band for wear and tension spring function.
Oil Pump Adjustment: Oil flow is adjustable via screw on bottom of saw. Turn clockwise to increase flow.

WARNING! Always use matched chain and bar specifications. A worn sprocket will rapidly wear a new chain.

Clutch & Drive

Centrifugal clutch assembly and drive shaft.

Component	Inspection & Service
Clutch Drum	Check for groove wear from chain. Replace if grooves are deep.
Clutch Shoes & Springs	Inspect shoes for wear and cracking. Check springs for fatigue or stretching.
Needle Bearing	Lubricate with high-temperature grease. Replace if rough or noisy.
Drive Shaft	Check splines for wear. Ensure bearing rotates smoothly.

Clutch engagement RPM: ~2800 rpm.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine will not start	No spark, flooded, fuel issue	Check spark, plug condition. Dry plug, choke off, pull with throttle open. Check fuel lines, filter, carburetor diaphragm.
Engine starts then dies	Fuel starvation, air leak	Clean fuel filter, check tank vent. Inspect crankcase seals and intake boot for leaks.
Lacks power under load	Clogged air filter, muffler, carb adjustment, compression loss	Clean air filter and spark arrestor. Adjust H screw. Check compression (should be >120 psi).
Chain does not turn	Clutch worn, brake engaged, sprocket seized	Inspect clutch shoes and springs. Disengage chain brake. Lubricate or replace sprocket bearing.
Excessive vibration	Unbalanced chain, loose components, AV mounts broken	Sharpen chain evenly. Tighten all fasteners. Inspect and replace anti-vibration rubber mounts.
Chain oils poorly	Clogged oil passages, faulty pump, wrong oil	Clean bar oil holes and saw outlet. Check oil pump drive and adjustment. Use proper bar & chain oil.

Torque Specifications

Cylinder Head Nuts: 10-12 Nm (7.5-9 ft-lbs)
Spark Plug: 20-25 Nm (15-18.5 ft-lbs)
Clutch Nut (Left-hand thread): 40-50 Nm (30-37 ft-lbs)
Flywheel Nut: 40-50 Nm (30-37 ft-lbs)
Guide Bar Nuts: 9-10 Nm (6.5-7.5 ft-lbs)
Muffler Bolts: 8-10 Nm (6-7.5 ft-lbs)

Exploded Views & Parts List

Refer to official Husqvarna parts catalog for detailed exploded views and part numbers for the 142 model. Common replacement parts include:

Air Filter: Part # 503 49 08-01
Fuel Filter: Part # 501 84 96-02
Spark Plug: Part # 503 87 96-02 (NGK BPMR7A)
Carburetor Repair Kit: Part # 530 03 61-02 (Zama C1U)
Clutch Assembly: Part # 537 33 40-01
Chain Brake Band: Part # 501 87 63-01

Service Support: For genuine parts and technical assistance, contact an authorized Husqvarna service dealer or visit www.husqvarna.com.