13.8.3 Standard Setting - Stihl MS 661 Manual

3. Use the low speed screw L
to set engine speed to
2,800 rpm.
4. Use the high speed screw H
to set engine speed to
13,000 rpm.
5. Remove tachometer after
obtaining engine speed of
13,000 rpm.
Turn high speed screw H
another 1/8 turn clockwise
(leaner),
a maximum engine speed
of 13,500 rpm is obtained –
making the setting any leaner
increases the risk of engine
damage.
The ignition module limits maximum
engine speed to 13,500 rpm. For
this reason the maximum
permissible engine speed cannot be
adjusted with a tachometer.
– Continue with "Securing the
limiter caps".
Securing the limiter caps
1
: Insert a suitable punch through
the holes (arrows) in the grommet
and push the limiter caps home
as far as stop.
This completes the basic setting of
the high speed screw (H) and the
low speed screw (L).
Version without limiter caps: The
high speed screw (H) and the low
speed screw (L) are now set.
110

13.8.3 Standard Setting

1
The limiter caps (1) must not be
removed for the standard setting.
Always perform the following steps
before carrying out any
adjustments:
– Troubleshooting, b 3.6
– 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
Standard setting with limiter caps
– Shut off the engine.
– Turn the high speed screw (H)
slowly counterclockwise as far as
1
stop, but not more than
3/4 of a turn.
– Turn the low speed screw (L)
slowly clockwise as far as stop,
but not more than a 3/4 turn, then
turn it back a 1/4 turn.
Check running behavior:
The engine must accelerate
smoothly when the throttle is
opened and run uniformly at idle
speed.
Standing setting without limiter
caps
– Shut off the engine.
– Starting with the high speed
screw (H) and low speed
screw (L) against their seats,
open them 1 full turn.
Check running behavior:
The engine must accelerate
smoothly when the throttle is
opened and run uniformly at idle
speed.
Adjusting idle speed
– Carry out "Setting".
Engine stops while idling
– Turn the idle speed screw LA
clockwise until the chain begins
to run, then turn it back
1 1/2 turns.
MS 661, MS 661 C-M