Trimmer

Stihl FS 90 R

4-Mix · Also known as: FS 90

The Stihl FS 90 R is a 28.4cc <!-- verify: stihlusa.com --> 4-Mix straight-shaft trimmer. Stihl's 4-Mix engine burns standard 50:1 premix fuel on a 4-stroke valve train, producing more torque at lower RPM with reduced noise and emissions compared to equivalent 2-stroke trimmers. It runs a Walbro carburetor <!-- verify: stihlusa.com --> and accepts Stihl trimmer heads and brush blades. Beyond standard air filter and fuel system service, 4-Mix models require periodic valve clearance checks approximately every 50 hours — an additional step absent on 2-stroke trimmers. Gearhead grease should be repacked annually under commercial use.