Stihl BG72 Blower Manual

The Stihl BG72 is a professional-grade backpack blower designed for demanding commercial and residential landscaping work. It features a powerful 2-stroke engine, ergonomic backpack harness system, variable speed throttle, cruise control, vibration damping, and a robust air filtration system. Below are key sections for safety, features, operation, maintenance, troubleshooting, and specifications.

Features at a Glance

Key components: 2-stroke engine, Backpack Harness, Throttle Lever, Cruise Control Lock, Air Filter Cover, Muffler, Fuel Tank, and Blower Tube.

Feature	Description
Engine Type	2-stroke, single-cylinder, air-cooled
Displacement	28.4 cc (1.73 cu. in.)
Power Output	1.1 kW (1.5 hp)
Fuel Tank Capacity	1.3 L (44 US fl. oz.)
Air Volume	Up to 765 m³/h (450 cfm)
Air Speed	Up to 322 km/h (200 mph)
Sound Power Level	112 dB(A)
Weight (dry)	9.5 kg (20.9 lbs)
Harness System	Padded backpack with adjustable straps
Throttle Control	Variable speed with cruise lock

Safety Information

Read and understand all instructions before operation.

1. Wear appropriate PPE: Safety glasses, hearing protection, long pants, closed-toe shoes.
2. Operate in well-ventilated areas only to avoid carbon monoxide poisoning.
3. Keep bystanders, pets, and children at least 15 meters (50 feet) away.
4. Never point the blower tube at people, animals, or breakable objects.
5. Inspect machine before each use for loose parts or damage.

WARNING! Gasoline is highly flammable. Refuel in a well-ventilated area with engine off and cool. Do not smoke.

Assembly & Setup

Unpack and inspect all parts. Assemble on a clean, flat surface.

1. Attach harness: Connect backpack frame to blower unit with provided bolts.
2. Install blower tube: Align tube with outlet, twist clockwise until it locks.
3. Adjust harness: Put on backpack, adjust shoulder and waist straps for comfort and balance.
4. Fuel mix: Prepare 50:1 gasoline to 2-stroke engine oil mixture (use STIHL HP Ultra or equivalent).
5. Initial start: Place unit on ground, set choke, prime bulb 5-10 times, pull starter cord firmly.

CAUTION! Ensure all fasteners are tight before operation. Do not operate with loose components.

Specifications

• Model: STIHL BG 72
• Engine: STIHL 2-MIX engine technology
• Displacement: 28.4 cm³
• Powerhead Weight: 5.2 kg (11.5 lbs)
• Total Weight (with harness): 9.5 kg (20.9 lbs)
• Fuel/Oil Ratio: 50:1 (Gasoline : 2-stroke oil)
• Recommended Fuel: Minimum 89 octane unleaded gasoline
• Sound Pressure Level: 96 dB(A) at operator's ear
• Vibration Levels (left/right): 4.5/5.5 m/s²
• Warranty: Limited commercial warranty - see dealer for details

Controls and Operation

Main Controls: Throttle Trigger, Stop Switch, Choke Lever, Primer Bulb, Cruise Control Lock.

Starting Procedure:

1. Set stop switch to "I" (Run) position.
2. Move choke lever to cold start position (closed).
3. Press primer bulb 5-10 times until fuel is visible.
4. Place unit on ground, hold handle firmly with one hand.
5. Pull starter cord briskly until engine fires (1-3 pulls).
6. Move choke lever to half-open position, pull starter again.
7. When engine runs, move choke to open position.
8. Allow 30-60 seconds warm-up before applying full throttle.

Operating Tips: Use cruise control for extended operation. Adjust harness for even weight distribution.

Fuel & Lubrication

Use fresh, unleaded gasoline with minimum 89 octane rating. Mix with STIHL HP Ultra 2-stroke oil at 50:1 ratio.

1. Always mix fuel in approved container, not in machine's tank.
2. Shake container thoroughly before refueling.
3. Clean area around fuel cap before opening.
4. Fill tank to 80% capacity to allow for expansion.
5. Wipe up any spilled fuel immediately.

Important: Never use automotive oil, diesel fuel, or premixed fuel older than 30 days. Stale fuel causes starting and performance problems.

Maintenance Schedule

Interval	Maintenance Task
Daily	Check for loose fasteners; Clean exterior; Inspect blower tube for damage
Every 10 hours	Clean air filter; Check spark plug condition
Every 25 hours	Clean spark arrestor screen; Check fuel filter
Every 50 hours	Replace air filter; Replace spark plug
Every 100 hours	Clean cooling fins; Check carburetor adjustment
Annually	Replace fuel filter; Clean fuel tank; Professional tune-up recommended

Air Filter Cleaning

A dirty air filter reduces performance and can cause engine damage.

1. Stop engine and allow to cool.
2. Press latch on air filter cover and remove cover.
3. Remove foam filter element from housing.
4. Wash filter in warm water with mild detergent.
5. Rinse thoroughly and squeeze out excess water (do not wring).
6. Allow filter to dry completely before reinstalling.
7. Apply STIHL filter oil evenly to filter surface.
8. Squeeze filter to distribute oil evenly.
9. Reinstall filter and cover securely.

Note: Replace heavily damaged or deteriorated filters immediately.

Spark Plug Service

Recommended spark plug: NGK BPMR7A (gap: 0.5 mm / 0.020 in).

1. Disconnect spark plug wire.
2. Clean around spark plug with compressed air.
3. Remove spark plug with appropriate socket.
4. Inspect electrode: Replace if worn, cracked, or fouled.
5. Set gap to 0.5 mm using feeler gauge.
6. Install new plug and tighten to 20 Nm (15 ft-lb).
7. Reconnect spark plug wire securely.

CAUTION! Never check for spark with plug removed and wire connected - risk of fire.

Storage Guidelines

Proper storage prevents fuel system problems and corrosion.

1. For storage up to 30 days: Add fuel stabilizer to fuel tank and run engine for 5 minutes.
2. For storage over 30 days: Drain fuel tank and carburetor completely.
3. Run engine until it stops from fuel starvation.
4. Remove spark plug and add 1 teaspoon of engine oil through spark plug hole.
5. Pull starter cord slowly 2-3 times to distribute oil.
6. Reinstall spark plug (do not connect wire).
7. Clean entire unit thoroughly.
8. Store in cool, dry place away from ignition sources.

Important: Never store with fuel in tank for extended periods without stabilizer.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine won't start	No fuel; Flooded; Bad spark plug	Check fuel level; Wait 10 minutes if flooded; Check/replace spark plug.
Engine starts then dies	Dirty air filter; Clogged fuel filter	Clean/replace air filter; Replace fuel filter.
Loss of power	Dirty spark arrestor; Clogged muffler	Clean spark arrestor screen; Remove carbon deposits from muffler.
Excessive vibration	Loose components; Damaged impeller	Tighten all fasteners; Inspect impeller for damage.
Air output reduced	Cracked blower tube; Debris in housing	Inspect tube for cracks; Clean housing and impeller area.
Hard to pull starter	Engine flooded; Piston seized	Remove spark plug, pull cord to clear cylinder; Seek professional service if seized.

Service: For repairs beyond basic maintenance, contact authorized STIHL dealer.

Support: STIHL USA - 1-800-467-8445 | www.stihlusa.com