Adjusting The Carburetor; 13.8.1 Basic Setting; 13.8.2 Setting - Stihl MS 661 Manual

Pre-installing limiter caps
1
: Push the new limiter caps (1)
onto the high speed screws as far
as the first detent (arrow) – do not
push them fully home.
– Carry out the basic setting,
b 13.8.1
13.8

Adjusting the Carburetor

13.8.1 Basic Setting

The basic setting is necessary only
if the high speed screw (H) or low
speed screw (L) has to be replaced
or after cleaning and adjusting the
carburetor from scratch.
It is necessary to carry out the basic
setting after removing the limiter
caps.
– Install the carburetor and air filter
– adjusting screws must be
preset and the new limiter caps
pre-installed.
– Check chain tension and adjust if
necessary.
– Inspect the spark arresting
screen (if fitted) and clean or
replace if necessary, b 3.7 or
b 6.1
– Check the air filter and clean or
replace if necessary, b 13.1
MS 661, MS 661 C-M
1
For the sake of clarity the adjusting
screws are shown on the exposed
carburetor.
: Insert the screwdriver (1)
5910 890 2304 through the pre-
installed limiter caps of high
speed screw (H) and low speed
screw (L).
: Starting with the high speed
screw (H) against its seat,
open it 1 1/2 turns
counterclockwise
: Starting with the low speed screw
(L) against its seat,
open it 1 full turn.
– Go to "Setting", b 13.8.2

13.8.2 Setting

– Insert screwdriver
5910 890 2304 through the
grommet and the pre-installed
limiter caps of high speed
screw (H) and low speed
screw (L).
Adjust engine speeds with
tachometer or STIHL MDG 1 engine
analyzer (select "Other STIHL
Products" / "Tachometer"). Adjust
specified engine speeds within a
tolerance of ± 200 rpm.
– Start the engine and warm it up
for 1minute at varying speeds. If
necessary, turn idle speed
screw (LA) slowly clockwise until
the engine runs smoothly – the
saw chain must not rotate.
Adjusting idle speed
1. Turn the low speed screw L
counterclockwise or clockwise
to obtain the highest engine
idle speed.
If this speed is between 3,300 rpm
and 3,500 rpm, continue with
step 3.
If this speed is outside the range
between 3,300 rpm and 3,500 rpm,
continue with step 2.
2. Use the idle speed screw LA
to set engine speed to
3,400 rpm and repeat step 1.
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