Adjusting The Carburetor - Stihl FS 90 Manual De Instrucciones

Adjusting the Carburetor

The carburetor comes from the factory
with a standard setting.
This setting provides an optimum fuel-air
mixture under most operating
conditions.
With this carburetor it is only possible to
adjust the high speed and low speed
screws within fine limits.
Standard Setting
Shut off the engine.
N
Mount approved cutting tool or
N
attachment.
Check the air filter and clean or
N
replace as necessary.
Check that the throttle cable is
N
properly adjusted – readjust if
necessary – see chapter on
"Adjusting the Throttle Cable".
Check the spark arresting screen
N
and clean or replace as necessary.
FS 90, FS 90 R
Carefully turn both adjusting screws
N
counterclockwise as far as stop:
– The high speed screw (H) is 3/4 turn
open.
– The low speed screw (H) is 3/4 turn
open.
Start and warm up the engine.
N
Adjust idle speed with the idle speed
N
screw (LA) so that the cutting
attachment does not move.
Fine Tuning
A slight correction of the setting of the
high speed screw (H) may be necessary
if engine power is not satisfactory when
operating at high altitude, sea level or
after changing the working tool.
Rule of thumb:
Turn the high speed screw (H) about
one quarter of a turn for every 3300 ft
(1000 m) change in altitude.
Conditions for adjustment
Carry out the standard setting
N
without disturbing the high speed
screw (H).
Warm up the engine for about 3
N
minutes.
Open the throttle wide.
N
At high altitude
Turn the high speed screw (H)
N
clockwise (leaner), no further than
stop, until there is no further
noticeable increase in engine
speed.
At sea level
Turn the high speed screw (H)
N
counterclockwise (richer), no further
than stop, until there is no further
noticeable increase in engine
speed.
It is possible that maximum engine
speed may be reached with the standard
setting in each case.
Readjust idle
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
Warm up the engine for about 3
N
minutes.
English
37