STIHL BR 420 Magnum Manual

The STIHL BR 420 Magnum is a professional-grade backpack blower designed for heavy-duty clearing and cleanup tasks. It features a powerful 2-stroke engine with STIHL anti-vibration system, adjustable shoulder straps, padded backrest, ergonomic controls, and a high-velocity air nozzle. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Safety Information 3. Assembly & Preparation 4. Technical Specifications 5. Controls and Operation 6. Fuel & Lubrication 7. Maintenance Schedule 8. Storage Guidelines 9. Troubleshooting 10. Warranty Information

Features at a Glance

Key components: STIHL 2-stroke engine, backpack harness system, throttle trigger with lock, choke control, air filter, spark plug, and blower tube with nozzle.

FeatureDescription
Engine TypeSTIHL 2-stroke, single-cylinder
Displacement40.2 cc
Power Output1.6 kW / 2.2 hp
Fuel Tank Capacity1.0 liter
Air VelocityUp to 85 m/s
Air VolumeUp to 900 m³/h
Sound Power Level112 dB(A)
Weight (dry)9.5 kg
Anti-Vibration SystemSTIHL standard
Harness SystemPadded, adjustable shoulder and waist straps

Safety Information

Read all instructions before operation. Wear appropriate PPE.

  1. Always wear eye and ear protection, sturdy gloves, and non-slip footwear.
  2. Operate in well-ventilated areas only; exhaust contains carbon monoxide.
  3. Keep bystanders, children, and pets at least 15 meters away.
  4. Inspect blower before each use for damage or loose parts.

WARNING! Never operate without proper personal protective equipment. Do not point nozzle at people, animals, or breakable objects.

Assembly & Preparation

Unpack and inspect all parts. Assemble according to diagram.

  1. Attach harness: Connect shoulder straps to mounting points on blower unit.
  2. Assemble blower tube: Connect tube sections and secure with locking collar.
  3. Attach nozzle: Slide nozzle onto tube end and tighten clamp.
  4. Fuel mixture: Use STIHL 2-stroke engine oil mixed with unleaded gasoline (50:1 ratio).
  5. Fill fuel tank: Use clean fuel container; avoid spills.

CAUTION! Ensure all connections are secure before starting engine.

Technical Specifications

Controls and Operation

Master control lever: STOP (0), START (full choke), RUN (half choke), NORMAL RUN. Throttle trigger with lock-out. Primer bulb for cold starts.

Starting Procedure:

  1. Place blower on flat, stable surface.
  2. Move master control lever to START (full choke).
  3. Press primer bulb 5-10 times until fuel is visible.
  4. Pull starter rope briskly until engine fires.
  5. Move lever to RUN (half choke) and pull starter again.
  6. Allow warm-up for 30 seconds before applying throttle.

Stopping: Move master control lever to STOP (0).

Fuel & Lubrication

Use only fresh unleaded gasoline (min. 89 octane) mixed with STIHL 2-stroke oil at 50:1 ratio.

  1. Mix fuel in approved container: Add oil first, then gasoline.
  2. Shake container thoroughly before filling.
  3. Never use fuel older than 30 days; avoid ethanol blends above 10%.
  4. Clean fuel cap area before opening to prevent contamination.

Tip: Store fuel mixture in labeled, airtight container away from heat and sunlight.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

  1. Daily: Check for loose fasteners, clean air filter, inspect spark plug.
  2. Weekly: Clean cooling fins, check fuel lines for cracks.
  3. Monthly: Clean spark arrestor screen, check carburetor settings.
  4. Seasonally: Replace fuel filter, inspect anti-vibration elements.
  5. Annually: Professional servicing recommended for commercial use.

WARNING! Always disconnect spark plug before performing maintenance.

Storage Guidelines

Prepare blower for storage if not used for more than 30 days.

  1. Drain fuel tank completely.
  2. Run engine until it stops to clear carburetor.
  3. Remove spark plug, add 1-2 drops of oil into cylinder, pull starter slowly 2-3 times, reinstall plug.
  4. Clean entire unit, especially cooling fins and air filter.
  5. Store in dry, dust-free location, covered with breathable cloth.

CAUTION! Never store with fuel in tank for extended periods.

Troubleshooting

SymptomPossible CauseCorrective Action
Engine won't startNo fuel, flooded, spark plugCheck fuel level; move choke to RUN; clean/replace spark plug.
Engine runs poorlyDirty air filter, old fuelClean air filter; replace with fresh fuel mixture.
Loss of powerClogged spark arrestor, fuel filterClean spark arrestor screen; replace fuel filter.
Excessive vibrationLoose parts, damaged impellerTighten all fasteners; inspect impeller for damage.
Airflow reducedTube blockage, worn nozzleClear debris from tube; inspect nozzle for wear.

Reset: For electronic ignition issues, disconnect spark plug wire for 1 minute.

Service: Authorized STIHL dealers only. Visit www.stihlusa.com for locations.

Warranty Information

STIHL Limited Warranty: 2 years for commercial use, 1 year for private use from date of purchase. Warranty covers defects in materials and workmanship. Not covered: normal wear, misuse, improper maintenance, non-STIHL parts. Keep original receipt. For claims, contact authorized STIHL dealer with proof of purchase.

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