User Adjustment, Carburetor With Limiter Cap - Stihl FC 75 Service Manual

9.4.3

User Adjustment, Carburetor with Limiter Cap

L
H
LA
Standard setting
The limiter cap must not be
removed from the high speed screw
(H) to carry out the standard setting.
With this carburetor it is only
possible to correct the setting of the
high speed screw (H) within fine
limits.
– Check the air filter and replace if
necessary, b 9.1
– Check the spark arresting
screen, clean or replace if
necessary, b 5.3
– Check throttle cable adjustment
(if fitted) and adjust if necessary,
b 8.8
– Mount the cutting tool,
attachment or CombiTool (KM)
properly.
FC 75, FC 85, FH 75, FS 75, FS 80, FS 85, HL 75, KM 85, KW 85
L
H
LA
Now make the following
adjustments:
: Turn the high speed screw (H)
counterclockwise as far as stop
(no more than 3/4 turn)
: Carefully turn the low speed
screw (L) clockwise until it is
against its seat, then open it one
full turn counterclockwise.
– Start the engine and allow it to
warm up.
: Use the idle speed screw (LA) to
adjust idle so that the tool does
not run.
A minor correction may be
necessary when operating at high
altitude or at sea level. Note that
even very slight corrections to the
high speed screw (H) produce a
noticeable change in engine
running behavior.
– Carry out the standard setting.
– Start the engine and allow it to
warm up.
– Open the throttle wide.
– At high altitude (mountains): Turn
the high speed screw (H)
clockwise (leaner), but no further
than stop, until there is no
noticeable increase in engine
speed.
It is possible that the standard
setting will produce the highest
engine rpm.
Adjusting idle speed
– Open the low speed screw (L)
one full turn.
– Allow the engine to warm up.
Engine stops while idling
– Turn the idle speed screw (LA )
slowly clockwise until the engine
runs smoothly.
Erratic idling behavior, poor
acceleration
– Idle setting is too lean. Turn the
low speed screw (L) counter-
clockwise (about a quarter turn)
until the engine runs and
accelerates smoothly.
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