Engine Management; Adjusting The Carburetor - Stihl HL 90 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.
HL 90 K

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
N Stopping the engine
N Inspect the cutting blades and clean
if necessary (they must be clean,
move freely and not be warped).
N Check that the throttle cable is
properly adjusted – readjust if
necessary – see chapter on
"Adjusting the Throttle Cable".
N Check the spark arresting screen
(not in all versions) and clean or
replace as necessary.
N Check the air filter and clean or
replace as necessary.
N Carefully turn both adjusting screws
counterclockwise as far as stop.
High speed screw (H) is open a 3/4 turn,
and the low speed screw (L) is open a
3/4 turn.
N Start and warm up the engine.
N
Adjust idle speed with the idle speed
screw (LA) so that the cutting
blades do not run.
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 or at sea level.
N Turn the high speed screw (H)
about one quarter turn for every
1000m change in altitude.
N Carry out the standard setting
without disturbing the high speed
screw (H).
English
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