Carburetor - Stihl BR 500 Service Manual

4.3

Carburetor

Condition
Carburetor floods, engine stalls
Poor acceleration
8
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
Diaphragm gasket leaking
Metering diaphragm damaged or
shrunk
Impulse hose damaged or kinked
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
upper face of housing
Turn low speed screw (L)
counterclockwise (richer) no further
than stop
Turn high speed screw (H)
counterclockwise (richer) no further
than stop
Set inlet control lever flush with
upper face of housing
Remove inlet needle, clean
and refit
Fit new diaphragm gasket
Fit new metering diaphragm
Fit new impulse hose
BR 500, BR 550, BR 600