Stihl MS 311 Manual page 14

3.6 Carburetor
Condition
Carburetor floods; engine stalls
Poor acceleration
MS 311, MS 391
Cause
Inlet needle not sealing
– foreign matter in valve seat or
cone
Inlet needle worn
Inlet control lever sticking on
spindle
Helical spring not located on nipple
of inlet control lever
Perforated disc on diaphragm is
deformed and presses constantly
against the inlet control lever
Metered diaphragm deformed
Setting of low speed screw too lean Check basic carburetor setting,
Setting of high speed screw too
lean
Inlet needle sticking to valve seat
Diaphragm gasket leaking
Metering diaphragm damaged or
shrunk
Tank vent faulty
Leak on fuel hose from tank to
carburetor
Remedy
Remove and clean the inlet needle,
clean the carburetor
Replace the inlet needle
Check the inlet control lever and
replace if necessary.
Remove the inlet control lever and
refit it correctly
Fit a new metering diaphragm
Fit a new metering diaphragm
correct if necessary
Check basic carburetor setting,
correct if necessary
Remove inlet needle, clean and
refit
Fit new diaphragm gasket
Fit a new metering diaphragm
Replace tank vent
Seal connections or install new fuel
hose
13