Fuel System - Stihl 029, 039 Service Manual

STIHL 029, 039
2.6

Fuel System

Note: For machines with automatic choke see 11.6.2.
Condition
Carburetor floods;
engine stalls
Poor acceleration
Engine will not idle,
idle speed too high
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 inlet control lever
Inlet control lever too high
(relative to design position)
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
Throttle shutter opened too wide
by idle speed adjusting screw
Remedy
Remove and clean or replace
inlet needle,
clean fuel tank, pickup body and
fuel line if necessary
Free off inlet control lever
Remove inlet control lever
and refit correctly
Fit new metering diaphragm
Set inlet control lever flush
with bottom of metering chamber
Back off low speed adjusting
screw slightly
(see Carburetor Adjustment)
Back off high speed adjusting
screw slightly
(see Carburetor Adjustment)
Set inlet control lever flush
with bottom of metering chamber
Remove inlet needle, clean
and refit
Clean bore
Fit new diaphragm gasket
Fit new metering diaphragm
Reset idle speed adjusting screw
correctly
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