SR 420 - Blower STIHL - Free user manual and instructions
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| Product Type | Backpack Blower |
| Brand | STIHL |
| Model | SR 420 |
| Engine Type | 2-Stroke |
| Displacement | 63.3 cc |
| Power Output | 4.0 kW |
| Fuel Tank Capacity | 1.6 L |
| Weight (without fuel) | 11.2 kg |
| Max Air Volume | 12.5 m³/min |
| Max Air Speed | 91 m/s |
| Noise Level (LwA) | 104 dB(A) |
| Vibration Level (left/right) | 3.0/3.0 m/s² |
| Carburetor Type | Rotary valve |
| Ignition System | Electronic magneto |
| Spark Plug | NGK BPMR7A |
| Fuel Mixture Ratio | 50:1 (gasoline:2-stroke oil) |
| Operating Principle | Single-cylinder, air-cooled |
| Recommended Use | Leaf and debris blowing |
| Maintenance Interval | After 10 hours of operation |
| Repairability | Modular design, spare parts available |
Frequently Asked Questions - SR 420 STIHL
How do I start the STIHL SR 420 blower?
Ensure the unit is on a flat surface. Set the choke lever to the closed position. Press the primer bulb 5-7 times until fuel is visible. Pull the starter rope slowly until resistance is felt, then pull sharply. Once the engine starts, open the choke gradually.
What fuel mixture does the SR 420 require?
Use a 50:1 ratio of unleaded gasoline (min. 90 octane) to high-quality 2-stroke oil, e.g., STIHL HP Ultra. Do not use pre-mixed fuels with ethanol.
What is the correct spark plug gap for the SR 420?
The recommended spark plug is NGK BPMR7A with a gap of 0.5 mm (0.020 in). Check and adjust if necessary.
How often should I clean the air filter?
Clean the air filter after every 10 hours of operation. In dusty conditions, clean more frequently. Wash with warm soapy water, rinse, and let dry thoroughly before reinstalling.
Can I use ethanol-blended fuel in my SR 420?
Avoid fuels with more than 10% ethanol (E10). Higher ethanol content can damage the engine and fuel system. Use premium unleaded gasoline with no ethanol if possible.
What is the recommended storage procedure for winter?
Empty the fuel tank and run the engine until it stops to prevent varnish buildup. Remove the spark plug and add a teaspoon of oil into the cylinder, then pull the starter rope slowly to distribute. Store in a dry, clean place.
How do I adjust the carburetor on the SR 420?
The carburetor is factory-set and should not be adjusted unless necessary. If adjustment is needed, use the idle speed screw (LA) and high-speed screw (H). Turn clockwise to lean, counterclockwise to richen. Seek professional help if unsure.
What safety gear should I wear when operating the blower?
Always wear eye protection, hearing protection, heavy-duty gloves, and sturdy shoes. Avoid loose clothing. Use a dust mask if blowing debris in dry conditions.
Where can I find replacement parts for my SR 420?
Authorized STIHL dealers carry original parts. You can also order online via the STIHL website or parts retailers. Use the model number (SR 420) and serial number for correct fit.
What is the warranty period for the STIHL SR 420?
STIHL offers a 2-year limited warranty for non-professional use. Professional use warranty may vary. Register your product online to activate coverage. Keep proof of purchase.
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USER MANUAL SR 420 STIHL
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Product information
Brand : STIHL
Model : SR 420
Category : Blower