FS 90 - Grass trimmer STIHL - Free user manual and instructions
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| Product Type | Gas-Powered Grass Trimmer |
| Engine Displacement | 30.1 cc |
| Engine Power | 1.2 kW (1.6 hp) |
| Fuel Type | Mixed gasoline (50:1 ratio) |
| Cutting Width | 41 cm (16 in) |
| Cutting Line Diameter | 2.7 mm (0.105 in) |
| Weight (without fuel and cutting attachment) | 5.3 kg (11.7 lbs) |
| Overall Length | 180 cm (71 in) |
| Handle Type | Bicycle handlebar |
| Anti-Vibration System | Yes |
| Cutting Tool Options | Line head, grass blade, brush knife |
| Throttle Control | Trigger with half-throttle lock |
| Fuel Tank Capacity | 0.5 L (17 fl oz) |
| Starter System | Easy2Start™ with electronic ignition |
| Maintenance Interval | Air filter cleaning every 25 hours, spark plug annually |
| Recommended Fuel Mix | STIHL 2-stroke oil at 50:1 |
| Safety Features | Stop switch, protective guard, throttle lock |
| Repairability | Modular design with replaceable parts (ignition, carburetor, handle) |
Frequently Asked Questions - FS 90 STIHL
What is the correct fuel mixture for the STIHL FS 90?
Use a 50:1 ratio of unleaded gasoline (89 octane or higher) to STIHL 2-stroke engine oil. Do not use pre-mixed fuels with ethanol content over 10%.
How do I start the FS 90 trimmer?
Set the stop switch to 'I' (on), move the choke lever to the closed position, press the primer bulb at least 5 times, pull the starter rope until the engine fires (up to 10 pulls), then open the choke and restart. Allow the engine to warm up before use.
Can I use a metal blade on the FS 90?
Yes, the FS 90 is compatible with STIHL grass blades and brush knives. Ensure you have the appropriate cutting head and guard. Always use a shoulder harness when using a blade.
How often should I replace the spark plug?
Replace the spark plug annually or after every 100 hours of operation. Use a NGK BPMR7A or equivalent. Check the gap is 0.5 mm (0.02 in).
What should I do if the trimmer won't start?
Check the fuel mix and level, ensure the stop switch is on, clean or replace the spark plug, clean the air filter, and verify the choke is operating correctly. If still not starting, consult a STIHL dealer.
How do I replace the cutting line on the FS 90?
Turn the bump head counterclockwise to remove. Pull out any remaining line, then insert a new 2.7 mm diameter line (about 6 m) into the holes. Wind evenly, leaving 15 cm tails. Reattach the head.
What is the proper way to store the trimmer?
Drain the fuel tank (run the engine until it stops) or add a fuel stabilizer. Store in a dry place away from direct sunlight. Clean the exterior and lubricate the cutting head.
Why does the engine stall under load?
This could be due to a dirty air filter, old fuel, or incorrect carburetor adjustment. Clean or replace the air filter, use fresh fuel, and if necessary, adjust the low-speed and high-speed screws as per the manual.
How do I maintain the air filter?
Every 25 hours, remove the air filter cover, take out the filter element, wash it in warm soapy water, let it dry thoroughly, and re-oil it with STIHL filter oil before reinstalling.
Is the FS 90 suitable for heavy brush?
The FS 90 is a semi-professional trimmer capable of handling light to medium brush. For heavy brush, consider a larger model or use the optional brush knife. Always wear protective gear.
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USER MANUAL FS 90 STIHL
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Product information
Brand : STIHL
Model : FS 90
Category : Grass trimmer