User Adjustment; Carburetor Without Limiter Caps - Stihl MS 650 Manual

12.4

User Adjustment

12.4.1 Carburetor without
Limiter Caps
Standard setting
– Shut off the engine.
– Check the air filter and clean or
replace as necessary.
– Check and clean or replace spark
arresting screen (if fitted).
– Check chain tension.
: Carefully screw down both
adjusting screws (H and L) until
they are against their seats.
Then make the following
adjustments:
: Open high speed screw (H)
one full turn.
: Open low speed screw (L)
one full turn.
If no tachometer is available, do not
turn the high speed screw (H)
beyond the standard setting to
make the mixture leaner.
80
Adjusting idle speed
– Adjust idle speed with a
tachometer. Adjust specified
engine speeds within tolerance
of +/- 200 rpm.
1. Adjust engine speed with idle
speed screw (LA) to 3,000 rpm.
2. Turn low speed screw (L)
counterclockwise to obtain
maximum engine speed.
If this speed is higher than
3,400 rpm, abort the procedure and
start again with step 1.
3. Use the idle speed screw (LA)
to set engine speed again to
3,000 rpm.
4. Set the engine speed to
2,500 rpm with the low speed
screw (L).
5. Open the throttle wide and set
maximum engine speed to
13,000 rpm with the high speed
screw (H).
Engine stops while idling
– Set the low speed screw (L) one
full turn open.
– Turn the idle speed screw (LA)
clockwise until the saw chain
begins to move. Then turn it back
one quarter turn.
Chain runs while engine is idling
– Set the low speed screw (L) one
full turn open.
– Turn the idle speed screw (LA)
counterclockwise until the chain
stops running. Then turn the
screw another one quarter turn in
the same direction.
Erratic idling behavior, poor
acceleration
Erratic engine running behavior
even though low speed screw (L) is
set one full turn open.
– Idle setting too lean. Turn the low
speed screw (L) counter-
clockwise 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).
MS 650, MS 660