Stihl MS 311 Manual page 15

Condition
Engine will not idle, idle speed too
high
Engine stops while idling
Saw chain rotates at idle speed
14
Cause
Throttle shutter opened too wide by
idle speed screw LA
Oil seals/engine housing leaking
Throttle shutter does not close
Air valve does not close
Idle jet bores
or ports blocked
Low speed screw too rich or
too lean
Setting of idle speed screw LA
incorrect – throttle shutter
completely closed
Tank vent faulty
Leak on fuel hose from tank to
carburetor
Engine idle speed too high
Clutch springs stretched or fatigued Replace the clutch springs or install
Clutch spring hooks broken
Remedy
Reset idle speed screw LA
correctly
Seal or replace oil seals/engine
housing
Replace throttle shutter and shaft
Replace end cover with air valve.
Clean the carburetor
Reset low speed screw L correctly
Reset idle speed screw LA
correctly
Replace tank vent
Seal connections or install new fuel
hose
Readjust with idle speed screw
LA (counterclockwise)
new clutch
Replace the clutch springs
MS 311, MS 391