Husqvarna 51 Chainsaw Manual

The Husqvarna 51 is a professional-grade chainsaw featuring a 2.5cc 2-stroke engine, automatic chain oiler, combined choke/stop control, inertia-activated chain brake, anti-vibration system, and quick-release air filter. Designed for demanding cutting tasks, it requires proper handling, maintenance, and safety precautions. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: Engine unit, guide bar, saw chain, chain brake, throttle trigger, choke/stop control, air filter, and fuel/oil tanks.

Safety Instructions

Always wear protective gear: helmet, goggles, hearing protection, gloves, chainsaw chaps, and sturdy boots.

1. Clear work area of obstacles and ensure secure footing.
2. Inspect chainsaw before each use for damage, loose parts, and chain tension.
3. Never operate with damaged or missing safety devices.
4. Keep bystanders at least 15 feet away.
5. Use both hands on handles; right hand on rear, left on front.

WARNING! Risk of severe injury or death from kickback. Maintain firm grip, do not cut with tip, and always engage chain brake when not cutting.

Assembly & Preparation

Unpack and inspect contents. Assemble guide bar and chain.

1. Attach guide bar: Loosen bar nuts, fit bar onto studs, align chain drive links with sprocket.
2. Fit chain: Place chain over bar, ensuring cutting teeth face forward on top.
3. Tension chain: Adjust tensioning screw until chain snaps back when pulled from bar.
4. Tighten bar nuts: Secure while lifting bar tip upward.
5. Fill tanks: Use Husqvarna 2-stroke oil mixed 50:1 with unleaded gasoline (min 89 octane). Fill chain oil with recommended bar & chain oil.

CAUTION! Chain must move freely; overtightening causes damage. Always check tension after initial run-in.

Specifications

• Engine Displacement: 2.5 cc (2.5 cm³).
• Power Output: 2.1 kW (2.8 hp).
• Fuel Consumption: Approx. 560 g/kWh.
• Idle Speed: 2,700 rpm.
• Maximum Power Speed: 9,000 rpm.
• Sound Pressure Level: 106 dB(A).
• Vibration Levels: Front handle 4.2 m/s², rear handle 4.8 m/s².
• Recommended Bar Length: 16"–20" (40–50 cm).
• Chain Pitch: 3/8" or .325".
• Spark Plug: Champion RCJ7Y or equivalent.

Controls and Functions

Front Handle: Chain brake lever, throttle trigger lockout. Rear Handle: Throttle trigger, choke/stop control, primer bulb (if equipped).

Controls: Choke/Stop Control (Cold start: choke; Run: horizontal; Stop: vertical), Throttle Trigger, Chain Brake Lever (forward to engage, pull back toward handle to disengage), Throttle Lockout (must be pressed to activate throttle), Decompression Valve (reduces starting effort).

Maintenance Points: Air filter cover, spark plug, cylinder cover, chain tensioner, oil filler cap, fuel filler cap.

Starting & Stopping

Cold Start:

1. Engage chain brake by pushing lever forward.
2. Set choke/stop control to choke position.
3. Press decompression valve (if equipped).
4. Place on ground, hold rear handle with right foot, left hand on front handle.
5. Pull starter cord sharply until engine fires (1-4 pulls).
6. Move choke/stop control to run position.
7. Pull starter cord again until engine starts.
8. Disengage chain brake before cutting.

Warm Start: Choke/stop control in run position; follow steps 4-8.

Stopping: Release throttle, move choke/stop control to stop position.

Cutting Techniques

Basic principles: Let chain do the work; avoid forcing saw.

1. Felling: Plan escape path (45° behind). Make notch cut (1/3 tree diameter), then felling cut leaving hinge.
2. Limbing: Stand uphill, cut branches from trunk with pulling chain (bottom of bar).
3. Bucking: Support log; cut from top for tension side, from bottom for compression.
4. Kickback Prevention: Hold saw firmly, do not cut with upper tip, maintain high chain speed.

Tip: Keep chain sharp; dull chain increases effort and kickback risk.

Maintenance Schedule

CAUTION! Disconnect spark plug before performing maintenance.

Chain & Bar Care

Sharpening: Use round file matching chain pitch (typically 5/32" or 7/32"). Maintain 30° filing angle; equalize strokes per cutter.

1. Secure bar; mark starting cutter.
2. File from inside out, maintaining angle and depth gauge clearance.
3. File all cutters on one side, then rotate saw to file opposite side.
4. Check depth gauges with gauge tool; file if above limit.
5. Clean bar groove weekly; flip bar monthly for even wear.

WARNING! Wear gloves when handling chain. Replace chain when stretched beyond adjuster limit or damaged.

Storage Guidelines

Long-term storage (over 30 days):

1. Empty fuel tank or add fuel stabilizer and run for 5 minutes.
2. Run carburetor dry by disconnecting fuel line and letting engine stall.
3. Remove chain, clean and soak in oil; clean bar groove and oil.
4. Clean entire saw; store in dry, cool place.
5. Remove spark plug, add teaspoon of oil, pull starter slowly 2-3 times, reinstall plug.

CAUTION! Never store with fuel in tank for more than 30 days; fuel degrades and damages carburetor.

Troubleshooting

Service: For repairs, contact authorized Husqvarna service center. Use genuine parts only.

Support: Husqvarna Forest & Garden Company, 1-800-487-5962, www.husqvarna.com