Stihl FS 90 Instruction Manual

Pages 116

Year 2016

Language(s)

of 116

Stihl FS 90 Specification

The Stihl FS 90 is a robust and versatile brush cutter designed for demanding landscaping tasks. It features a powerful 28.4 cc, 4-MIX engine, which combines the benefits of a 4-stroke engine with the simplicity of a 2-stroke engine, offering efficient fuel consumption and reduced emissions. The engine delivers consistent power and torque, making it suitable for heavy-duty trimming and cutting.

Equipped with a solid drive shaft, the FS 90 provides reliable power transfer and durability, ensuring long-lasting performance. The machine includes a multi-function control handle that enhances user comfort by allowing easy access to all operating elements without the need to release the handle. An adjustable bike handle design further facilitates ergonomic handling and control, particularly useful for extended periods of operation.

For enhanced usability, the FS 90 incorporates Stihl’s anti-vibration system, which significantly reduces operator fatigue by minimizing engine vibrations. The cutting head can be easily switched between a metal blade and a nylon line, providing flexibility for various cutting tasks such as trimming grass, weeds, or thicker brush.

The air filter system in the FS 90 is designed for longevity, with a pre-separation air filtration mechanism that extends the cleaning intervals, ensuring the engine remains in optimal condition. The fuel tank is transparent, allowing operators to easily monitor fuel levels during use.

Overall, the Stihl FS 90 is engineered for professional landscapers and demanding homeowners who require a reliable, efficient, and adaptable tool for a variety of trimming and cutting needs. Its combination of power, ergonomic design, and versatile cutting capabilities make it a preferred choice for those seeking durability and high performance in outdoor power equipment.

Stihl FS 90 F.A.Q.

How do I start the Stihl FS 90 trimmer?

To start the Stihl FS 90, set the choke lever to the cold start position, pump the fuel primer bulb several times until fuel is visible, pull the starter cord until the engine fires, then move the choke to the run position and pull again to start.

What is the recommended maintenance schedule for the Stihl FS 90?

Regular maintenance includes checking and cleaning the air filter after every 10 hours of use, inspecting the spark plug every 25 hours, and replacing it if necessary. Additionally, inspect the fuel system and lubricate the gearbox every 50 hours.

How can I troubleshoot if the FS 90 engine won't start?

First, check the fuel tank for sufficient fuel. Ensure the spark plug is clean and properly gapped. Verify that the air filter is not clogged. If the engine still doesn’t start, inspect the ignition coil and replace it if faulty.

What type of fuel should I use in the Stihl FS 90?

Use a high-quality, unleaded gasoline with a minimum octane rating of 89, mixed with Stihl 2-cycle engine oil in a ratio of 50:1. Avoid using ethanol-rich fuels to prevent engine damage.

How do I replace the trimmer line on the FS 90?

To replace the trimmer line, remove the trimmer head cover, pull out the old line, insert the new line through the holes, wind it evenly in the direction indicated, and reattach the cover securely.

What should I do if the FS 90 vibrates excessively during use?

Excessive vibration can be caused by an unbalanced trimmer head or worn-out bearings. Check that the trimmer head is properly balanced and replace any damaged parts. Inspect the drive shaft and bearings for wear and replace if necessary.

How often should I clean the air filter on my FS 90?

The air filter should be checked and cleaned after every 10 hours of operation or more frequently in dusty conditions. A clean air filter ensures optimal engine performance and longevity.

What is the correct spark plug gap for the Stihl FS 90?

The correct spark plug gap for the Stihl FS 90 is 0.5 mm (0.020 inches). Use a feeler gauge to measure and adjust the gap if necessary to ensure efficient ignition.

How do I adjust the carburetor on the FS 90?

To adjust the carburetor, locate the idle speed and mixture screws. Turn the idle speed screw clockwise to increase idle speed or counterclockwise to decrease it. Adjust the mixture screw for optimal performance by turning it slowly until the engine runs smoothly.

Why is my FS 90 losing power during operation?

Power loss can be caused by a clogged air filter, a dirty spark plug, or fuel issues. Check and clean the air filter, replace the spark plug if it’s worn, and ensure the fuel is fresh and mixed correctly. Clean the exhaust port and muffler if carbon build-up is suspected.