Engine Management; Adjusting The Carburetor - Stihl MS 290 Instruction Manual

Engine Management

Exhaust emissions are controlled by the
design of the fundamental engine
parameters and components (e.g.
carburation, ignition, timing and valve or
port timing) without the addition of any
major hardware.
MS 290, MS 310, MS 390

Adjusting the Carburetor

Basic information
The carburetor comes from the factory
with a standard setting.
The carburetor has been adjusted for
optimum performance and fuel
efficiency in all operating states.
The high speed screw alters the
engine's power output and the maximum
off-load engine speed.
If you make the setting too lean it will
increase the risk of engine damage
through lack of lubrication and
overheating.
Standard setting
Switch off engine
N
Check the air filter – clean or replace
N
it if necessary.
Check the spark arresting screen in
N
the muffler (present only in some
countries) – clean or replace it if
necessary.
Carburetors with H = 1 and L = 1
Carefully turn both adjusting screws
N
clockwise until they are seated
firmly (clockwise)
Turn the high speed screw (H) 1 full
N
turn counterclockwise
Turn the low speed screw (L) 1 full
N
turn counterclockwise
Carburetor with H = 3/4 and L = 1/4
Turn the high speed screw (H)
N
counterclockwise as far as possible
(max. 3/4 turn)
Carefully turn the low speed
N
screw (L) clockwise – as far as
possible – then back off 1/4 turn.
English
29