Carburetor - Stihl 4180 Series Manual

4.4

Carburetor

Condition
Carburetor floods; engine stalls
Poor acceleration
10
Cause
Inlet needle not sealing. Foreign
matter in valve seat or cone
damaged
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
Inlet control lever too high (relative
to design position)
After more than five starting
attempts with choke shutter closed
Idle jet too lean
Main jet too lean
Inlet control lever too low (relative
to design position)
Inlet needle sticking to valve seat
Connecting bore to atmosphere
blocked
Diaphragm gasket leaking
Metering diaphragm damaged or
shrunk
Remedy
Remove and clean or replace inlet
needle, clean fuel tank, pickup
body and fuel hose if necessary
Free off inlet control lever
Remove the inlet control lever and
refit it correctly
Fit new metering diaphragm
Set inlet control lever flush with
upper face of housing or bottom of
metering chamber
Open choke shutter after no more
than five starting attempts
Back off low speed screw slightly
Back off high speed screw slightly
Set inlet control lever flush with
upper face of housing or bottom of
metering chamber
Remove inlet needle and clean
valve seat
Clean bore
Fit new diaphragm gasket
Fit new metering diaphragm
Series 4180 Powerhead