To Adjust Carburetor; Preliminary Setting; Final Setting; Acceleration Test - Craftsman 917.252451 Owner's Manual

;ERVICE AND ADJUSTMENTS
ACCELERATION TEST -
TO ADJUST CARBURETOR (See Fig. 30)
The carburetor has been preset at the factory and adjust-
ment should not be necessary. However, minor adjust-
ment may be required to cornpensate for differences in fuel,
temperature, altitude or load. If the carburetor does need
adjustment, proceed as follows:
In general, turning idle mixture valve in (clockwise) de-
creases the supply of fuel to the engine giving a leaner fuel/
air mixture. Turning the idle mixture valve out (counter-
clockwise) increases the supply of fuel to the engine giving
a richer fuel/air mixture.
IMPORTANT: DAMAGE TO THE NEEDLE VALVE AND
THE SEAT IN CARBURETOR MAY RESULT IF SCREW IS
TURNED IN TOO TIGHT.
PRELIMINARY SETTING -
• Air cleaner assembly must be assembled to the carbu-
retor when making carburetor adjustments,
o Be sure the throttle control cable is adjusted properly
(see above).
o With engine off turn idle mixture valve in (clockwise)
closing it finger tight and then turn out (counterclock-
wise) 1 full turn.
FINAL SETTING -
o Start engine and allow to warm for five minutes. Make
final adjustments with engine running and shift/motion
control lever in neutral (N) position.
, Move throttle control lever to slow (,<!) position° With
finger, rotate and hold throttle lever against idle speed
screw. Turn idle speed screw to attain 1750 RPM.
o While still holding throttle lever against idle speed
screw, turn idle mixture valve in (clockwise) until en-
gine begins to die and then turn out (ccurtterclockwise)
until engine runs rough. Turn valve to a point midway
between those two positions Release throttle lever,
o Move throttle control lever from slow (,_.) to fast (,_)
position. If engine hesitates or dies, turn idle mixture
valveout (counterclockwise) 1/8turn. Repeattest and
continue to adjust, if necessary, until engine acceler-
ates smoothly.
High speed stop is factory adjusted. Do not adjust -
damage may result,
IMPORTANT: NEVER TAMPER WITH THE ENGINE
GOVERNOR, WHICH IS FACTORY SET FOR PROPER
ENGINE SPEED. OVERSPEEDING THE ENGINE ABOVE
THE FACTORY HIGH SPEED SETTING CAN BE
DANGEROUS. IF YOU THINK THE ENGINE-GOVERNED
HIGH SPEED NEEDS ADJUSTING, CONTACT YOUR
NEAREST AUTHORIZED SERVICE CENTER/
DEPARTMENT, WHICH HAS PROPER EQUIPMENT AND
EXPERIENCE TO MAKE ANY NECESSARY
ADJUSTMENTS.
THROTTLE
LEVER
IDLE SPEED
SCREW
....
IDLE MIXTURE VALVE
FIG. 30
24