30
English / USA
FS 500, FS 550
The carburetor comes from the factory
with a standard setting.
This setting provides an optimum fuel-air
mixture under most operating
conditions.
Standard Setting
: Shut off the engine.
: Mount approved cutting tool.
: Check the air filter and clean or
replace it if necessary.
: Check spark arresting screen* and
clean or replace if necessary.
: Turn high speed screw (H)
counterclockwise as far as stop, i.e.
1/4 turn from max. lean setting.
: Turn low speed screw (L) clockwise
as far as stop – then back off the
screw one quarter of a turn.
: Start and warm up the engine.
: Adjust idle speed with the idle speed
screw (LA) so that the cutting tool
does not rotate.
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, at sea level or
after changing the cutting tool.
* see “Guide to Using this Manual”
Rule of thumb:
Turn high speed screw (H) about
1
/
4
turn for every 3300 ft (1000m)
change in altitude.
At high altitude
: Turn high speed screw (H) clock-
wise (leaner) no further than stop
until there is no noticeable increase
in engine speed.
At sea level
: Turn high speed screw (H) counter-
clockwise (richer) no further than
stop until there is no noticeable
increase in engine speed.
It is possible that maximum engine
speed may be reached with the
standard setting in each case.
Adjusting Idle Speed
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.
Engine stops while idling
: Turn idle speed screw (LA) slowly
clockwise until the engine runs
smoothly – the cutting tool must not
rotate.
Adjusting the Carburetor
LA
H
L
398BA020 KN
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