Stihl FS 91 FS 91 R Instruction Manual

Pages 124

Year 2020

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of 124

Stihl FS 91 FS 91 R Specification

The Stihl FS 91 and FS 91 R are professional-grade trimmers designed for efficient landscape maintenance, equipped with advanced features to enhance performance and ease of use. Both models are powered by a robust 28.4 cc 4-MIX® engine, blending the benefits of a 2-stroke and 4-stroke engine to deliver powerful performance with reduced emissions and improved fuel efficiency. The FS 91 features a straight shaft design, while the FS 91 R is designed with a loop handle, offering greater maneuverability and precision in tight spaces.

These trimmers are engineered with a simplified starting system, incorporating a semi-automatic choke lever and a one-touch stop switch, facilitating easier and more reliable starting. The multi-function control handle allows operators to access all controls with one hand, optimizing user comfort and safety. Additionally, the FS 91 and FS 91 R come with a large fuel tank capacity of 24 oz, allowing for extended operation times without frequent refueling.

Durability is a key aspect of the design, with a rigid drive shaft enhancing longevity and reducing maintenance needs. The ergonomic design, featuring an anti-vibration system, minimizes operator fatigue, making them suitable for prolonged use. Both models are compatible with a variety of cutting attachments, providing versatility for different trimming tasks. The FS 91 and FS 91 R are ideal for professional landscapers and demanding users seeking reliable performance and efficiency in their outdoor power equipment.

Stihl FS 91 FS 91 R F.A.Q.

What is the correct fuel mixture for the Stihl FS 91 R?

The Stihl FS 91 R requires a 50:1 fuel mixture, which is 50 parts gasoline to 1 part 2-cycle engine oil.

How do I replace the trimmer line on the Stihl FS 91 R?

To replace the trimmer line, remove the spool from the trimmer head, wind new line onto the spool in the direction indicated, and reattach it to the trimmer head.

What type of spark plug is used in the Stihl FS 91 R?

The Stihl FS 91 R uses an NGK CMR6H spark plug.

How often should I clean the air filter on my Stihl FS 91 R?

It is recommended to clean the air filter after every 10 hours of use or more frequently in dusty conditions.

What should I do if my Stihl FS 91 R won't start?

Check the spark plug, ensure the fuel is fresh and properly mixed, inspect the air filter, and verify that the stop switch is in the "on" position.

How can I adjust the idle speed on the Stihl FS 91 R?

The idle speed can be adjusted by turning the idle speed screw (marked “LA”) on the carburetor. Refer to the manual for the correct procedure.

What maintenance should be performed regularly on the Stihl FS 91 R?

Regular maintenance includes checking and cleaning the air filter, replacing the spark plug annually, inspecting the fuel system, and sharpening the cutting blades.

How can I replace the cutting blade on the Stihl FS 91 R?

To replace the cutting blade, ensure the trimmer is off, remove the blade by releasing the mounting nut, and install the new blade securely with the nut.

What safety gear should be worn when operating the Stihl FS 91 R?

Operators should wear protective glasses, ear protection, gloves, long pants, and sturdy footwear while using the trimmer.

How do I store the Stihl FS 91 R during the off-season?

Empty the fuel tank, clean the tool, remove the cutting attachment, and store it in a dry, secure place away from direct sunlight.