:
WARNING:
Carbon monoxide fumes can be
fatal! Do not make any adj ustments
to the carburetor in a confined area
such as a storage building. Move the
tractor outside into the air.
682 and 782 Tractors
NOTE: Air cleaner has been removed from illustra-
tions in order to show carburetor.
Adjusting the High-Speed Adjustment Screw
Turn the high speed adjustment screw counter-
clockwise approximately two turns from the
closed position and start the engine. Refer to
figure 20.
Be sure the choke is fully open (knob fully in)
when adjusting.
After the engine has reached normal operatingtemperature,
place the throttle lever in the fast
position and turn the high speed adjustment
screw clockwise to the leanest mixture that will
allow satisfactory acceleration and steady gover-
nor operation. Then, turn counterclockwise to the
richest mixture that allows satisfactory operation.The
difference between the rich and lean points is
about V2 turn. Set the mixture to the rich end of
this range.
If the engine misses and backfires under load, the
high speed mixture is too lean. The high speed ad-
justment screw must be turned counterclockwise
1/8 turn at a time until the condition is corrected.
If the engine shows a sooty exhaust and is slug-
gish under load, the high speed mixture is toorich.
The high speed adjustment screw must be
turned clockwise 1/8 turn at a time until the condi-
tion is corrected.
Adjusting the Idle Adjustment Screw
After the high speed ajdustment screw is ad-justed,
it may be necessary to readjust the idle ad-
justment screw as each affects the other. Refer to
figure 20.
Close the idle adjustment screw to its seat by
turning it clockwise; then open it one turn. Start
the engine and operate it at fast idling speed
(without any load) until thoroughly warm.
While the engine is running at fast idle speed, it is
advisable to screw in the throttle stop screw a few
turns to keep the engine from stopping when the
throttle lever is moved to the fully retarded
"SLOW" position. The engine will then be idling at
a fairly high speed and the throttle stop screw can
be backed out a little at a time until the desired
idle speed is obtained (1800 RPM).
If the engine misses or rolls while backing out the
throttle stop screw, the idle adjustment screw
may be adjusted in or out until the engine
operates smoothly. Speed up the engine for a few
seconds; then recheck the idle adjustment. A
slight adjustment in or out will give the smoothest
idle.
FIGURE 21.
1. Main fuel screw
2. Idle fuel screw
3. Idle speed screw
If readjustment becomes necessary, stop the
engine, then turn the MAIN and IDLE fuel ad-
justing screws all the way in, until they bottom
lightly. Refer to figure 21.
Main Fuel Adjustment
Preliminary setting-turn screw out 2V2 turns.
Final setting-start engine and raise engine
speed to maximum governed, no load speed. Turn
screw in just until engine speed decreases and
note the position of the screw. Now turn the screw
out. The engine speed will first increase, but then
decrease as screw is turned out. Note the position
of screw when engine speed starts to decrease.
Set the screw midway between the t,wo points
noted above.
Idle Speed Adjustment
Run engine at maximum governed, no load speed
for a minimum of 30 seconds, then allow engine
speed to fall to idle or put throttle into idle posi-tion.
Set engine speed to 1200 (:t 75 RPM) by turn-
ing the idle speed screw in or out.
Idle Fuel Adjustment
Set the idle fuel mixture by turning the idle fuel
screw out, from the closed position, 3/4 to 1 fullturn.
15
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