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SERVICE AND ADJUSTMENTS
t
Carburetor adjustment iscritical and if done improperly
can permanently damage the engine as well as the car-
buretor. Please read all instructions and consult the
Troubleshooting section of this manual before begin-
ning this process. Ifthe engine does not operate accord-
ing to these instructions after repeating the adjusting
steps, do not use the unit.for further assistance, please
call our customer assistance hotline at !-800-235-5878.
_ WARNING:
MAKECARBURETORADJUSTMENTSWITHTHE
LOWERENDSUPPORTEDTO PREVENTBLADE
OR SEMI-AUTOMATICFROMCONTACTINGANY
OBJECT.HOLDUNITWITHYOURHAND.
THE BLADE OR SEMI-AUTOMATICHEAD WILL
BE SPINNINGDURINGMOST OFTHIS PROCE-
DURE.WEARYOUR PROTECTIVEEQUIPMENT
ANDOBSERVEALLSAFETYPRECAUTIONS.
KEEPOTHERSAWAYWHENMAKINGCARBURE-
TORADJUSTMENTS.
IN "LOW SPEED MIXTURE ADJUSTMENT,"
RECHECKIDLESPEEDAFTER EACH ADJUST-
MENT.THEBLADEOR SEMI-AUTOMATICHEAD
MUSTNOTMOVEATIDLESPEED.
CONTACTYOUR SEARS SERVICE CENTER IF
THE IDLE SPEED SETTING CANNOT BE
ADJUSTEDSO THAT THE BLADE STOPS AT
IDLE.DONOTUSETHEUNITUNTILITHAS BEEN
PROPERLYADJUSTEDOR REPAIRED.
engine does not start, it may be flooded. If in doubt, read
the section on flooded engine in the starting section of this
manual prior to beginning any adjustments.
If you are unsure about adjusting the carburetor or experi-
ence any problem whileattempting this process, please call
the 1-800 number listed on thefront cover of this manual for
further assistance,
The carburetor has been adjusted at the factory for sea level
conditions. Adjustments may become necessaryif the unit is
used at significantly higher altitudes or ff you notice any of
thefollowing conditions:
• Blade or semi.automatichead moves when the engine
runs at idle speed. See "Idle speed adjustment."
• Engine will not idle.See"Idle speed adjustment"and "Low
speed mixture adjustment."
• Engine dies or hesitateswhen it shouldaccelerate. See
"Acceleration adjustment:'
• Loss of cuttingpowerwhichis not corrected,byair filter
cleaning.See "High speedmixtureadjustment:
NOTE: Do notattempttoadjust the screwbeyond the stops
as damage can occur.
CARBURETOR PRESETS (Fig. 43)
The Carburetorhas threeadjusting screws:
L = Low speed mixtureadjustingscrew
H= High speed mixture adjustingscrew
T = Idlespeed adjustingscrew
If yourengine willnot startdue to suspected impropercar-
buretor adjustment,thefollowing presetsmay be required.If
used,itis recommendedthata!lsteps withinthe adjustment
procedure be completedin order to assure a properly set
carburetor.Ifpresetsarenotneeded,proceedtosection"Idle
speed adjustment."
Very small adjustmentscan affectengine performance.It is
importantto turnthescrewa verysmall amountper adjust-
ment and test performancebefore making further adjust-
ments.Each adjustmentshouldbe no morethanthe widthof
the slot in the adjusting screw.
• Turn both ofthe mixturescrews counterclockwise untilthey o
stop. DOnot attempt to adjust the screw beyond the stops
- 29 -
as damage can occur.
• Turnidlespeed screw clockwise 1/2 turn.
• Startthe engine and operate forthree(3) minutesto warm
up.Go to "Adjusting procedure"
ADJUSTING PROCEDURE
IDLE SPEED ADJUSTMENT
• Allow the warmengine to idle.
• Adjust the idle speed screw until the engine continues to
run withoutsta,ing and withoutthe blade or semi-auto:
matichead turning.
- Turnscrew clockwise to increase engine speedif engine
stalls or dies.
-Turn screw counterclockwise to slow engine down
and/or to keep the blade or semi-automatic head from
turning.
• No furtheradjustments are necessary if blade or semi-
automatic head does not turn at idle speed and if perfor-
mance Lssatisfactory.
•HIGH SPEED LOW SPEED
MIXTURE ,_ MIXTURE SCREW
IDLE SPEED SCREW
Figure 43
LOW SPEED MIXTURE ADJUSTMENT
• AUowengineto idle.
• Turn the low speed mixture screw slowlyclockwiseuntil
theRPM starts to drop. Note the position.
• Turnthe low speed mixture screwslowly counterclockwise
untifthe RPM speeds up and startsto drop again.Note the
posit{on.
• Set the low speed mixture screwat the midpoint between
thetwopositions.
HIGH SPEED MIXTURE ADJUSTMENT
IMPORTANT: DO NOT OPERATE ENGINE AT FULL
THROTTLE FOR PROLONGED PERIODS WHILE MAK-
ING HIGH SPEED ADJUSTMENTS AS DAMAGETO THE
ENGINECAN OCCUR.
• Makea test cutin grass.
• Basedon performanceof the unitwhilecutting,adjust the
highspeed mixture screw in 1/16turn incrementsas fol-
lows:
- Clockwiseif unitsmokesor losespower whilecutting.Do
not adjust for best power by sound or speed, butjudge
by how wet/the unit performs during operation.
- Counterclockwise if the unithasspeed whilenot cutting,
butdies or lacks power while cutting.
• Repeatthe test cut in grass.
• Continuewith 1/16 turn adjustments untilthe unit perfor-
mance isacceptable whilecutting.
• After completingadjustments, check for acceleration.
• Ifunitaccelerates properly no further adjustmentsare nec-
essary.If not, proceed to acceleration check.
ACCELERATION CHECK
• Iftheenginediesor hesitatesinsteadofaccelerating, turn
the lowspeed mixture screw 1/16ofa turnat a timecoun-
terclockwiseuntilyou have smoothacceleration.
• Check the idle speed for stabilityand that the btade or
semi-automatichead does notturn.Adjustas necessary.
Recheckforsmoothaccelerationand stableidle.
Repeatprocessas necessary foracceptableperformance.
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