Carburetor With Limiter Caps - Stihl MS 650 Manual

Adjustments for operation at
high altitude
A minor correction may be
necessary if engine power is not
satisfactory when operating at high
altitude.
– Check standard setting.
– Warm up the engine.
– Turn high speed screw (H) very
slightly clockwise (leaner).
If the setting is made too lean there
is a risk of engine damage due to
insufficient lubrication and
overheating.
MS 650, MS 660
12.4.2 Carburetor with
Limiter Caps
Standard setting
The limiter caps must not be
removed for the standard setting.
– Check the air filter and clean or
replace as necessary.
– Check and clean or replace spark
arresting screen (if fitted).
– Check chain tension.
– With this carburetor it is only
possible to correct the settings of
the high speed screw (H) and low
speed screw (L) within fine limits.
– Open the high speed screw (H)
counterclockwise as far as stop.
– Close the low speed screw (L)
clockwise as far as stop, then
open it one quarter turn counter-
clockwise.
Adjusting engine idle speed
Engine stops while idling
– Set the low speed screw (L) one
quarter 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
quarter 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 is set
one quarter turn open.
– Idle setting too lean. Turn the low
speed screw (L) counter-
clockwise, 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).
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