Engine Management; Adjusting The Carburetor - Stihl MS 291 C-Q Manual De Instrucciones

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 291 C-Q

Adjusting the Carburetor

General Information
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
correct the adjusting screws within fine
limits.
If the setting is too lean there is a
risk of engine damage due to
insufficient lubrication and
overheating.
Standard Setting
H
L
LA
N Stopping the engine
N Check the air filter and clean or
replace if necessary.
N Check the spark arresting screen
(country-specific) in the muffler and
clean or replace if necessary.
N Turn the high speed screw (H)
counterclockwise as far as stop (no
more than 3/4 turn).
N
Turn the low speed screw (L)
carefully clockwise as far as stop,
then turn it back 1 full turn.
Readjust idle
Engine stops while idling
N Open the low speed screw (L) one
full turn.
N
Turn the idle speed screw (LA)
clockwise until the chain begins to
run – then back it off 1 full turn.
Chain runs when engine is idling
N Open the low speed screw (L) one
full turn.
N Turn the idle speed screw (LA)
counterclockwise until the chain
begins to run – then turn it another
1 turn in the same direction.
If the chain continues moving
when the engine is idling, have
your saw checked and repaired by
your servicing dealer.
Erratic idling behavior, poor
acceleration (even though low speed
screw is open one turn)
N Idle setting is too lean: Turn the low
speed screw (L) counterclockwise
until the engine runs and
accelerates smoothly.
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
English
41