Motor Management; Adjusting The Carburetor - Stihl HS 81 Instruction Manual

English

Motor 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.
18

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
adjust the high speed screw within fine
limits.
Standard Setting
: Shut off the engine.
: Check the air filter and clean or
replace if necessary.
: Check the spark arresting screen
(not fitted in all markets) in the
muffler and clean or replace if
necessary.
: Turn the high speed screw (H)
counterclockwise as far as stop (no
more than 3/4 turn).
: Carefully screw the low speed
screw down onto its seat
(clockwise).
: Open the low speed screw (L) one
full turn.
Adjusting Idle Speed
Engine stops while idling
: Check standard setting.
: Turn the idle speed screw (LA)
slowly clockwise until the cutting
blades begin to run – then turn the
screw back 2 1/2 turns.
Cutting blades run when engine is
idling
: Check standard setting.
: Turn the idle speed screw (LA)
slowly counterclockwise until the
cutting blades stop running – then
turn the screw another 2 1/2 turns in
the same direction.
HS 81 R, HS 81 T