To Adjust Carburetor; Preliminary Setting; Final Setting; Acceleration Test - Craftsman 3One 917.254860 Owner's Manual

SEFIVICE AND ADJUSTMENTS
TO ADJUST CARBURETOR
(See Fig. 33 & 34)
The carburetor has been preset at the factory and adjust-
ment should not be necessary. However, minor adjustment
may be required to compensate for differences in fuel,
temperature, altitude or lead. If the carburetor does need
adjustment, proceed as follows:
In general, turning the mixture screw in (clockwise) de-
creases the supply of fuel to the engine giving a leaner fuel/
air mixture. Turning the mixture screw out (counterclock-
wise) increases the supply of fuel to the engine giving a
richer fuel/air mixture.
_MPORTANT: DAMAGE TO THE NEEDLES AND THE
SEATS IN CARBURETOR MAY RESULT IF SCREW IS
TURNED iN TOO TIGHT.
PRELIMINARY SETTING -
- Be sure you have a clean air filter, and the throttle
control cabte and choke are adjusted properly (see
above).
- With engine off turn idle mixture screw in (clockwise)
closing it finger tight and then turn out (counterclock-
wise) 1-1/4 to 1-1/2 turns.
FINAL SE-t-FtNG -
° Start engine and allow to warm for five minutes. Make
final adjustments with engine running and shift! motion
control lever in "NEUTRAL" position.
= With throttle control lever in "SLOW" position, hold
throttle lever against idle speed screw and adjust idle
speed screw to obtain 1200 to !400 RPM.
Whife still holding throttle lever against idle speed
screw, turn idle mixture screw in (clockwise) until
engine begins to die and then turn out (counterclock-
wise) until engine runs rough. Turn screw to a point
midway between those two positions.
o Continue to hotd throttle lever against idle speed screw
and adjust idle speed screw to obtain 900 to 1200 RPM.
Release throttle lever.
ACCELERATION TEST
o Move throttle control lever from "SLOW" to "FAST"
position. If engine hesitates or dies, turn idle mixture
screw out (counterclockwise) 1/8 turn. Repeat test
and continue to adjust, if necessan], untit engineaccel-
erates smoothly.
High speed stop is factory adjusted. Do not adjust- damage
may result.
IMPORTANT: NEVER TAMPER WITH THE ENGINE
GOVERNOR, WHICH tS FACTORY SET FOR PROPER
ENGINE SPEED. OVERSPEEDING THE ENGtNE ABOVE
THE FACTORY HIGH SPEED SETTING CAN BE
DANGEROUS. IF YOU THfNKTHE ENGINE_GOVERNED
HIGH SPEED NEEDS ADJUSTING, CONTACT YOUR
NEAREST AUTHORIZED SERVICE CENTER, WHtCH HAS
PROPER EQUIPMENT AND EXPERIENCE TO MAKE ANY
NECESSARY ADJUSTMENTS.
IDLE SPEED
SCREW
IDLE MIXTURE
SCREW
F_G. 33
IDLE SPEED
SCREW
/
THROTTLE
LEVER
_E MIXTURE
SCREW
FiG. 34
24