Stihl FS 90 User Manual

41FS 90, FS 90 R
English / USA
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 for about
3 minutes.
Engine stops while idling
: Turn idle speed screw (LA) slowly
clockwise until the engine runs
smoothly – the tool must not rotate.
Cutting tool rotates when engine is
idling
: Turn idle speed screw (LA) slowly
counterclockwise until the tool stops
rotating and then turn the screw
about another
1
/
2
to
3
/
4
turn in the
same direction.
Erratic idling behavior, engine stops
even though setting of LA screw is
correct, poor acceleration
Idle setting too lean:
: Turn low speed screw (L)
counterclockwise (no further than
stop) until the engine runs and
accelerates smoothly.
Erratic idling behavior
Idle setting too rich:
: Turn low speed screw (L) clockwise
(no further than stop) until the
engine runs and accelerates
smoothly.
The spark arresting screen is an option
that is not fitted in all machines.
: If the engine is low on power, check
the spark arresting screen in the
muffler.
: Wait for muffler to cool down.
: Move slide control to STOP-O.
: Remove the screw (1).
: Remove the screws (2).
: Lift away the shroud (3).
Spark Arresting Screen in
Muffler
249BA059 KN
1
2
3
2
249BA060 KN

Stihl FS 90 Specifications

General

Engine Displacement	28.4 cc
Fuel Type	Gasoline
Handle Type	Loop handle
Shaft Type	Straight
Fuel Capacity	0.53 l
Weight	5.8 kg
Cutting Attachment	Autocut 25-2
Engine Power	0.95 kW (1.27 bhp)