Carburetor - Stihl 090 Instruction Manual / Owners Manual

Carburetor
1
~
High
speed adjustment screw
2 ~
Low speed adjustment
SCf9W
The cartluretor Is adjusted at the factory foy maximum
performance and most econOmic fuel consumption under
average local atmospheric conditions. When working
at
high altitudes (mountains) or near sea level the carburetor
may need to be readjusted. This must be done with two
aQjustment screws and the Idle speed regulating screw.
Basic adjustment of the carburetor.
High speed adjustment screw (H): short,
1 tum open
Low speed adjustment screw (L): long,
1 tum open
Take this basic adjustment as a guide when readjusting
your carburetor. Check carburetor adjustment with warm
engine and a clean air filter. Carefully screw In both adJust-
me. n t
screw
until snug litl
Notes for fine adjustment of carburetor
Engine stops while Idling:
Tum idle speed adjustment screw slightly clockwise while
the engine Is running (chain must not tum).
Chain turns while engine Is Idling:
Tum idle speed adjustment screw slightly counter-clock-
wise.
Engine runs erratically at Idle speed:
Adjust at low speed adjustment screw. Tum clockwise for
leaner mixture or counter-clockwise for richer mixture.
Gautlon: The setting of the high-speed adjustment screw
affects the engine's maximum off-load speed,
~ ~
Is set too
lean (adjustment screw turned too far clockwise), the maxi-
mum permissible engine speed of 6000 r.p.m. will be
exceeded. This can
resu~
in engine damage brought about
by insufficient lubrication In particular.
Apart from minor readjustments, you should not attempt
carburetor adjustments or repairs yourself. Entrust such
work to STIHL Service. In most areas you will find STIHL
Service Shops
w~h
trained specialists and the tools neces-
sary for expert servicing.
31