72 MS 290, MS 310, MS 390
Standard setting
Do not remove the limiter cap to
carry out the standard setting.
– With this carburetor it is only
possible to correct the settings of
the high speed screw (H) and low
VA
209RA053
speed screw (L) within fine limits
Make the following adjustments:
–
Close high speed screw (H) by
turning it clockwise as far as stop,
then open it 3/4 turn counter-
clockwise.
– Close the low speed screw (L) by
turning it clockwise as far as stop,
then open it 1/4 turn counter-
clockwise.
Adjusting idle speed
Engine stops while idling
– Open the low speed screw L
one quarter of a turn.
– 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
– Open the low speed screw L
one quarter of a turn.
– Open the idle speed screw LA
counterclockwise until the chain
stops running – then turn the
screw another full turn in the
same direction.
Erratic idling behavior, poor
acceleration
Irregular idling or poor acceleration
even though the low speed screw is
set to one quarter turn open.
– Idle setting too lean. Turn the low
speed screw L counterclockwise,
but no further than stop, 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.
Adjustment for operation at high
altitude or at sea level
A slight correction of the setting may
be necessary if engine power is not
satisfactory when operating at high
altitude or at sea level.
– Check the standard setting.
– Warm up the engine.
At high altitude (mountains)
– Turn the high speed screw H
clockwise (leaner), no further
than stop.
At sea level
– Turn the high speed screw H
counterclockwise (richer), no
further than stop.
If the setting is too lean there is a
risk of engine damage due to
insufficient lubrication and
overheating.
11.4.2 User Adjustment
(Carburetor with Limiter
Caps)
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