Carburetor - Stihl MS 661 Manual

3.6

Carburetor

Condition
Carburetor floods; engine stalls
Poor acceleration
MS 661, MS 661 C-M
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
Low speed screw L and / or high
speed screw H too lean
Models with M-Tronic, carburetor
setting too lean
Inlet needle sticking to valve seat
Metering diaphragm or gasket
damaged
Tank vent faulty
Leak in fuel hose between pickup
body and 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
Check basic carburetor setting,
correct if necessary
Check M-Tronic with STIHL MDG 1
and troubleshooting chart, b 8.7,
adjust or calibrate control unit,
b 8.1
Remove inlet needle, clean and
refit
Fit a new metering diaphragm and
gasket
Fit new tank vent
Seal connections or install new fuel
hose
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