Sears 917.299642 - Manual (Page 20)

SERVICE AND ADJUSTMENT
CARBURETOR
NOTE: A dirty Air Cleaner will cause the Engine to lun
rough. Be sure Air Cleaner is dean before adjustments.
Factory settings are satisfactory for most applications
and conditions, if adjustments are needed, proceed as
follows:
Never attempt to change maximum Engine speed. This
is preset at the faptory and should only be changed by a
qualified service technician who has the necessary
equipment The Carburetor mixture may need re-adjust­
ing if Engine lacks power or does not idle properly.
MIXTURE ADJUSTMENT
• Turn Needle Valve {Fig. 33} clockwise until it just
closes. Valve may be damaged by turning Needle Valve
in too far,
• Open Needle Valve 1-1/2 turns counterclockwise
This initial adjustment will permit the Engine to be
started and warmed up prior to final adjustment,
• Start the Engine,. Allow Engine to warm up for about 5
minutes before proceeding,.
• Place Throttle Control in "IDLE" position,
• Turn Needle Vaive in until Engine slows (clockwise
{rH) lean mixture).
• Next turn Needle Valve out past smooth operating point
until Engine runs unevenly (counterclockwise rich
mixture).
• Now turn Needle Valve to the midpoint between rich
and lean so the Engine runs smoothly.
IDLE RPM ADJUSTMENT
■ To adjust idle RPM, Rotate Throttle Linkage counter­
clockwise (r^) and hold against stop while adjusting
idle Speed Adjusting Screw to obtain 1750 RPM. Re­
lease Throttle Linkage,
CHECKING ADJUSTMENT
• Test the Engine by tilling, If Engine dies out, it usually
indicates that the mixture is slightly lean and it may be
necessary to turn the Needle Valve counterclockwise
(»^} slightly to provide a richer mixture. This richer
mixture may cause a slight unevenness in idling
THROTTLE CONTROL CABLE ADJUSTMENT
CAUTION: NEVER TAMPER WITH THE ENGINE GOV­
ERNOR. WHICH IS FACTORY SET FOR
PROPER ENGINE SPEED.
• Loosen Throttle Cable Adjusting Screw.
• With Throttle Control in "FAST' position and Cable con­
nected to Bellcrank, pull Cable backward through Screw
until Bellcrank is as far rearward as it will go.
• Tighten Adjusting Screw
THROTTLE
LINKAGE
THROTTLE
STOP
SPARK PLUG
WIRE
IDLE SPEED
ADJUSTING
SCREW
BELLCRANK•
FIGURE 33
20