Adjusting Carburetor; User Adjustment (Carburetor Without Limiter Caps) - Stihl MS 290 Manual

11.4

Adjusting Carburetor

11.4.1 User Adjustment (Carburetor without Limiter Caps)

Standard setting
(without tachometer)
To readjust the carburetor, start with
the standard setting.
– 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.
Standard setting
(with tachometer)
– Check the air filter and clean or
replace as necessary.
– Check and clean or replace spark
arresting screen (if fitted).
– Check chain tension.
– Warm up the engine.
– Adjust idle speed.
MS 290, MS 310, MS 390
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 3,300 rpm.
2. Turn low speed screw (L)
clockwise or counterclockwise
to obtain maximum engine
speed.
If this speed is higher than
3,700 rpm, abort the procedure and
start again with step 1.
3. Use the idle speed screw (LA)
to set engine speed again to
3,300 rpm.
4. Set the engine speed to
2,800 rpm with the low speed
screw (L).
Starting from the standard setting,
use the high speed screw (H) to
adjust the maximum engine speed
to:
12,500 rpm (MS 290)
13,000 rpm (MS 310, 390)
If the setting is too lean there is a
risk of engine damage due to
insufficient lubrication and
overheating.
Engine stops while idling
– Turn the idle speed screw LA
clockwise until the chain begins
to run – then turn the screw back
one quarter of a turn.
Chain runs when engine is idling
– Turn the idle speed screw LA
counterclockwise until the chain
stops running – then turn the
screw another quarter turn in the
same direction.
Erratic idling behavior, poor
acceleration
– Idle setting too lean. Turn the low
speed screw L counterclockwise
until the engine speed drops –the
turn the screw back one quarter
of a turn.
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