Stihl MS 171 Manual page 15

4.6 Carburetor
Condition
Carburetor floods;
engine stalls
Poor acceleration
14
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Cause
Inlet needle not sealing. Foreign
matter between valve seat and
cone or cone 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
Setting of low speed screw too lean Check basic carburetor setting,
High speed screw too rich
Inlet needle sticking to valve seat
Diaphragm gasket leaking
Metering diaphragm damaged or
shrunk
Manifold damaged
Remedy
Remove and clean or replace the
inlet needle, clean the carburetor,
replace inlet needle if necessary
Clean inlet control lever, replace if
necessary
Remove the inlet control lever and
refit it correctly
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 new metering diaphragm
Install new manifold
MS 171, MS 181, MS 211