Carburetor - Stihl FS 94 Instruction Manual

3.4

Carburetor

Condition
Carburetor floods; engine stalls
Poor acceleration
3.5
Series 4149 Powerhead
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 metering
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
Metering diaphragm gasket leaking Fit new diaphragm gasket
Metering diaphragm damaged or
shrunk
Tank vent faulty
Leak in fuel hose from tank to
carburetor
Remedy
Remove and clean the inlet needle,
clean the carburetor
Fit new inlet needle
Check the inlet control lever and
replace if necessary
Remove the inlet control lever and
refit it correctly
Fit new metering diaphragm
Fit new metering diaphragm
correct if necessary
Check basic carburetor setting,
correct if necessary
Remove inlet needle, clean and
refit
Fit new metering diaphragm
Fit new tank vent
Seal connections or install new fuel
hose
11