stihl mist blower sr 450 manual

The STIHL SR 450 Mist Blower is a professional-grade, backpack-mounted unit designed for applying liquid chemicals, pesticides, and fertilizers over medium to large areas. It features a powerful 4.2 HP engine, an adjustable 4.2-gallon polyethylene tank, a telescopic discharge tube, and multiple nozzle options for precise application control. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 4.2 HP STIHL 2-stroke engine, 4.2-gallon (16 L) polyethylene tank, adjustable shoulder straps, telescopic discharge tube, rotary air pump, multiple nozzle tips, and ergonomic control handle.

Assembly & Preparation

Unpack all components and inspect for damage. Assemble on a clean, flat surface.

1. Attach shoulder straps: Connect straps to designated mounting points on tank frame.
2. Install discharge tube: Insert telescopic tube into blower housing and secure locking collar.
3. Attach nozzle: Select desired nozzle tip and screw onto end of discharge tube.
4. Install control handle: Mount onto discharge tube at comfortable operating height.
5. Fuel mixture: Prepare STIHL 2-stroke engine oil mixed with unleaded gasoline (50:1 ratio).

WARNING! Always wear appropriate Personal Protective Equipment (PPE) including gloves, goggles, and respirator when handling chemicals. Assemble in a well-ventilated area.

First-Time Operation

Perform pre-operation checks before starting the engine.

1. Check all fasteners: Ensure all screws, nuts, and connections are tight.
2. Inspect hoses and seals: Look for cracks, leaks, or damage.
3. Fill fuel tank: Use fresh fuel/oil mixture (50:1).
4. Prime engine: Press primer bulb 5-7 times until fuel is visible.
5. Set choke: Move to cold start position.
6. Start engine: Place unit on ground, hold securely, pull starter cord briskly.
7. Warm up: Allow engine to run at idle for 1-2 minutes before applying throttle.

CAUTION! Never operate without proper PPE. Keep bystanders at least 50 feet away during operation.

Specifications

• Engine Type: STIHL 2-stroke, single cylinder, air-cooled.
• Displacement: 2.1 cu in (34.6 cm³).
• Power Output: 4.2 HP (3.1 kW).
• Fuel/Oil Ratio: 50:1 (unleaded gasoline to STIHL 2-stroke oil).
• Chemical Tank: 4.2 gal (16 L) polyethylene, with fill opening and strainer.
• Maximum Airflow: 1060 cfm (500 m³/h).
• Liquid Output: Adjustable from 0.05 to 3.2 gal/min (0.2-12 L/min).
• Sound Power Level: 107 dB(A).
• Vibration Levels: Left handle: 3.2 m/s², Right handle: 4.5 m/s².

Controls and Settings

Main controls located on handle and engine housing.

Engine Controls: STOP switch (OFF/RUN), Choke lever (Cold start/Warm start/Run), Primer bulb, Throttle trigger lockout, Throttle trigger. Blower Controls: Shut-off valve (controls chemical flow), Air volume adjustment (via throttle), Nozzle selection (changes spray pattern).

Adjustable settings: Shoulder strap length, Discharge tube length (telescopic), Nozzle type (fan, cone, jet), Chemical flow rate (via valve).

Mixing & Filling Chemicals

Always follow chemical manufacturer's instructions for mixing ratios and safety.

1. Put on PPE: Gloves, goggles, respirator, and protective clothing.
2. Clean tank: Rinse with water if previously used.
3. Mix chemicals: In separate container per manufacturer's directions.
4. Fill tank: Use funnel and strainer to prevent clogging.
5. Secure cap: Tighten tank cap firmly.
6. Pressurize: Pump pressure bulb (if equipped) to 10-15 psi.

Tip: Mix only amount needed for immediate use. Never mix different chemicals unless specified compatible.

Operating Procedures

Proper technique ensures effective application and operator safety.

1. Don PPE: Complete protective gear including respirator.
2. Start engine: As outlined in First-Time Operation.
3. Adjust straps: For comfortable, balanced fit.
4. Open chemical valve: Turn knob to begin flow.
5. Begin application: Use steady sweeping motion, maintaining consistent distance from target.
6. Adjust throttle: For desired air volume and droplet size.
7. Change direction: Work so wind carries mist away from operator.
8. Shut down: Close chemical valve, allow engine to run briefly to clear lines, then turn off engine.

WARNING! Never point discharge tube at people, animals, or food sources. Avoid inhalation of mist.

Maintenance Schedule

Regular maintenance ensures optimal performance and longevity.

CAUTION! Always disconnect spark plug before performing maintenance. Allow engine to cool completely.

Storage & Transport

Proper storage prevents damage and chemical contamination.

1. Drain chemicals: Completely empty chemical tank.
2. Triple rinse: Flush tank and lines with clean water.
3. Run with water: Operate briefly to clear all chemical residues.
4. Drain fuel: Run engine until it stops to empty carburetor.
5. Clean exterior: Wipe down entire unit.
6. Store: In cool, dry place away from children and ignition sources.
7. Transport: Secure in vehicle to prevent tipping or damage.

CAUTION! Never store with chemicals in tank. Always transport in upright position.

Safety & Regulatory Information

Complies with ANSI B175.2 and EPA regulations for pesticide application equipment. Contains components that may be subject to California Proposition 65 warnings. Engine meets EPA Phase 2 emission standards. Always follow local regulations regarding chemical application, including notification requirements, buffer zones, and record keeping. For technical support, contact STIHL at 1-800-467-8445 or visit www.stihlusa.com.

Troubleshooting

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

Support: 1-800-467-8445; www.stihlusa.com