Kohler K91 Service Manual page 39

I dle Speed
Adjusting Screw
Figu re 6-1 8. Fixed Main Jet Carburetor.
Adjust
To M idpoint
Figure 6-1 9. Carburetor Adjustment .
CARBURETOR ADJ USTMENT
NOT E : The tip of the low idle fuel and high idle
fuel adjusting needles are tapered to critical di­
mensions . Damage to the needles and the seats
in carburetor body will result if the needles are
forced.
I dle Fuel
Adjusting Needle
4 .
Place t h e throttle into the " fast " position . If possi­
Lean
Turn the high idle fuel adjusting needle
terclockwise) from the preliminary setting until the
engine speed decreases (rich) . Note the position
of the needle.
Now turn the adjusting needle
engine speed may increase, then it will decrease
as the needle is turned in (lean ) . Note the position
of the needl e .
Set t h e adjusting needle
and lean settings. See Figure 6-2 1 .
5 .
" NOTE : The actual low idle speed depends on the
applicatio n . Refer to the equipment manufacturer' s
instructions f o r specific l o w idle speed settin gs.
The recommended low idle speed for Basic En­
gines is 1 200 rpm . To ensure best results when
setting the low idle fuel needle. the low idle speed
must not exceed 1 500 rpm .
In general , turning the adjusting needles I n (clock­
wise) decreases the supply of fuel to the carbure­
tor. This gives a leaner fuel-to-air mixture . Turning
out
the adjust f ng needles
creases the supply of fuel to the carburetor. This
gives a richer fuel-to-air mixture . Setting the
midway
needles between the lean and rich posi­
tions will usually give the best results.
Adjust the carburetor as follows :
1 . With the engine stopped , turn the low idle fuel
in
adjusting needle (clockwise) u ntil it bottoms
lightly.
Preliminary Settings:
2 .
dles out (counterclockwise) from lightly bot­
tomed according to the table shown in Figure
6-20 .
Start the engine and run a t half throttle for five
3 .
to ten minutes to warm u p . The engine must
be warm before making final settings (Steps 4 ,
5 , 6 , and 7) .
High Idle Fuel Needle Setting:
is required only for adjustable high Idle (main)
Jet carburetors. If the carburetor is a fixed main
Jet type, go to step 5 .
ble , place the engine under load .
Low Idle Speed Settin g :
control into the " idle " or " slow" position. Set
the low idle speed to
rpm) by turning the low idle speed adjusting
in or out.
screw Check the speed using a ta­
chometer.
(counterclockwise) in­
Turn the adjusting nee­
This adjustment
out
(coun­
i n
(clockwise) . The
midway
between t h e rich
Place the throttle
1 200 rpm
(+ or - 75
*
6. 1 3