Husqvarna 257 Chainsaw Parts Manual
The Husqvarna 257 Chainsaw is a professional-grade chainsaw known for its power, reliability, and durability. This manual provides detailed parts identification, assembly instructions, maintenance procedures, and troubleshooting guidance to ensure safe operation and optimal performance. Below are key sections covering safety, parts diagrams, specifications, maintenance, and ordering information.
Parts at a Glance
Key components: Engine assembly, Ignition system, Fuel system, Air filter, Chain brake, Guide bar, Saw chain, Clutch, Starter assembly, and Handle system.
| Component Group | Description |
|---|
| Engine Assembly | Cylinder, piston, crankshaft, bearings, seals |
| Ignition System | Spark plug, ignition coil, flywheel, stop switch |
| Fuel System | Fuel tank, carburetor, fuel lines, filter, primer bulb |
| Air Filter | Air filter element and cover |
| Chain Brake | Brake band, handle, activation mechanism |
| Guide Bar & Chain | Guide bar, saw chain, drive sprocket, tensioner |
| Clutch Assembly | Clutch drum, springs, shoes, bearing |
| Starter Assembly | Recoil starter, rope, pulley, spring |
| Handle System | Front and rear handles, antivibration mounts |
| External Covers | Top cover, side covers, chain brake cover |
Safety Information
Always prioritize safety when handling, assembling, or maintaining the chainsaw.
- Personal Protective Equipment (PPE): Always wear chainsaw chaps, gloves, eye protection, hearing protection, and sturdy boots.
- Pre-Operation Check: Inspect chain sharpness, tension, and lubrication. Ensure all parts are secure and undamaged.
- Fuel Safety: Refuel in a well-ventilated area, away from ignition sources. Use approved fuel mix (50:1 gasoline to 2-stroke oil).
- Chain Brake Test: Test the chain brake functionality before each use.
WARNING! Never operate a chainsaw with damaged, loose, or missing parts. Disconnect the spark plug before performing any maintenance.
Parts Diagrams & Lists
Refer to the exploded view diagrams for part identification and numbers.
- Cylinder & Piston Group: Includes cylinder, piston, rings, wrist pin, and circlips.
- Crankcase & Crankshaft: Includes crankcase halves, crankshaft, main bearings, and seals.
- Carburetor & Air Filter: Includes carburetor assembly, gaskets, throttle linkage, air filter, and cover.
- Ignition System: Includes flywheel, ignition coil, spark plug, and wiring.
- Chain Brake Assembly: Includes brake band, handle, springs, and activation lever.
- Guide Bar & Chain: Includes guide bar, saw chain, drive sprocket, bar nuts, and tensioning screw.
- Clutch & Drum: Includes clutch assembly, drum, and bearing.
- Starter Assembly: Includes recoil housing, rope, pulley, and spring.
- Handles & Controls: Includes front/rear handles, throttle trigger, lockout, and antivibration elements.
- External Covers: Includes top cover, side cover, and chain brake cover with fasteners.
Note: Use the official Husqvarna part numbers when ordering replacements.
Specifications
- Model: Husqvarna 257
- Engine Displacement: 56.5 cc (3.45 cu. in.)
- Power Output: 3.5 kW (4.7 hp)
- Fuel Tank Volume: 0.85 L (1.8 US pints)
- Oil Tank Volume: 0.35 L (0.74 US pints)
- Recommended Bar Lengths: 15" to 20" (38 cm to 50 cm)
- Chain Pitch: 3/8" or .325"
- Chain Gauge: 0.058" (1.5 mm) or 0.063" (1.6 mm)
- Weight (Powerhead): 6.2 kg (13.7 lbs) without bar and chain
- Ignition System: Electronic, air gap 0.3 mm (0.012")
- Spark Plug: Champion RCJ7Y or equivalent, gap 0.5 mm (0.020")
- Fuel/Oil Ratio: 50:1 (2% high-quality 2-stroke oil)
Assembly Instructions
For new saw assembly or major component replacement.
- Handle Installation: Attach front and rear handles to crankcase using provided bolts and antivibration mounts. Torque to specification.
- Guide Bar & Chain: Place bar on studs, loop chain over sprocket and bar. Adjust tension so chain snaps back when pulled from bar.
- Clutch & Sprocket: Install drive sprocket and clutch assembly onto crankshaft. Secure with retaining nut.
- Starter Assembly: Align recoil starter with crankcase posts. Secure with screws.
- Covers: Install side cover and chain brake cover, ensuring all linkages engage properly.
CAUTION! Use correct torque values. Overtightening can damage components.
Maintenance Procedures
Regular maintenance ensures longevity and safe operation.
Daily/Pre-Use: Check chain sharpness and tension. Check bar lubrication. Inspect for loose nuts/bolts. Clean air filter.
Weekly/10 Hours: Clean cooling fins. Check spark plug condition and gap. Clean fuel filter. Inspect chain brake function.
Monthly/50 Hours: Clean carburetor air passage. Check fuel lines for cracks. Inspect clutch and sprocket for wear. Check antivibration mounts.
Annually/100 Hours: Decarbonize cylinder exhaust port. Check crankshaft seals. Replace fuel filter. Inspect piston and rings through exhaust port.
Carburetor Adjustment
The carburetor has three adjustment screws: L (Low speed), H (High speed), T (Idle).
- Initial Settings: Gently turn L and H screws clockwise until seated, then back out 1 turn each. Set T screw for a steady idle.
- Warm Up: Start saw and let it run at half throttle for 5-10 minutes to reach operating temperature.
- Idle (T) Adjustment: Adjust T screw so chain does not move at idle, but engine runs smoothly.
- Low Speed (L) Adjustment: Turn L screw for fastest, smooth idle. Then enrich slightly (counter-clockwise) until idle just begins to slow.
- High Speed (H) Adjustment: With saw at full throttle (no load), turn H screw to achieve maximum RPM as per specification (approx. 13,000 RPM). Do not over-lean.
WARNING! An improperly adjusted carburetor can cause severe engine damage. Final adjustment should be performed with a tachometer.
Chain & Bar Maintenance
Proper care of the cutting system is critical for performance and safety.
- Sharpening: Use correct round file size for chain pitch. Maintain correct filing angle (typically 30°). File all cutters to equal length.
- Tensioning: Chain should be snug against bar but pull freely. Re-tension when chain feels loose (check frequently when new).
- Bar Care: Regularly clean bar groove and oil holes. Flip bar weekly for even wear. Dress bar rails with a flat file if burred.
- Lubrication: Always use high-quality bar & chain oil. Ensure oiler is working and tank is filled.
Tip: A sharp, well-tensioned chain reduces kickback risk and operator fatigue.
Troubleshooting
| Symptom | Possible Cause | Corrective Action |
|---|
| Engine will not start | No spark, flooded, fuel issue | Check spark plug, ignition coil gap. Check fuel lines, filter, carburetor. Use correct starting procedure. |
| Engine starts but dies | Clogged fuel filter, carb adjustment, air leak | Replace fuel filter. Check carburetor settings. Inspect crankcase seals and intake manifold for leaks. |
| Loss of power | Clogged air filter, exhaust screen, bad piston/rings | Clean/replace air filter. Clean spark arrestor screen. Inspect cylinder through exhaust port. |
| Chain does not turn | Clutch worn, sprocket worn, brake engaged | Inspect clutch shoes and springs. Check drive sprocket. Ensure chain brake is disengaged. |
| Excessive vibration | Loose components, unbalanced chain, bad mounts | Tighten all bolts/nuts. Balance chain by sharpening evenly. Check antivibration mounts. |
| Chain throws oil | Over-oiling, wrong oil viscosity | Check oiler adjustment. Use recommended bar & chain oil. |
| Chain runs at idle | Idle speed too high, clutch sticking | Adjust idle (T) screw lower. Clean clutch drum and shoes of sawdust and oil. |
Reset: For electronic ignition issues, disconnect spark plug wire, wait 1 minute, reconnect.
Parts Ordering
Use genuine Husqvarna parts for optimal performance and safety.
- Identify Part Number: Use the diagrams and lists in this manual to find the correct part number.
- Authorized Dealer: Contact your local Husqvarna authorized service dealer.
- Online: Visit the official Husqvarna website parts portal.
- Information Needed: Provide model number (257), serial number, and part number.
Note: Non-genuine parts may void warranty and compromise safety.
Warranty Information
Husqvarna provides a limited warranty for the 257 chainsaw. The warranty covers defects in material and workmanship under normal use and proper maintenance.
- Consumer Warranty: Typically 2 years for private users from date of purchase.
- Professional Warranty: Typically 90 days for commercial use from date of purchase.
- What is Covered: Repair or replacement of defective parts.
- What is Not Covered: Damage from misuse, neglect, improper maintenance, use of non-genuine parts, or normal wear items (chain, bar, spark plug, filters).
- Claim Procedure: Contact the authorized Husqvarna dealer where the product was purchased with proof of purchase.
For support, visit www.husqvarna.com or contact your local authorized Husqvarna dealer.
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