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CARBURETOR ADJUSTMENTS
WARNING
When making adjustments to the carburetor
while the engine is running, disengage the PTO
clutch and engage the brake pedal lock. Keep
clear of all moving parts and be careful of all hot
surfaces.
WARNING
Carbon monoxide fumes can be fatal! Do not
make any adjustments to the carburetor in a
confined area such as a storage building. Move
the tractor outside into the air.
The carburetor is adjusted at the factory and under
normal operating conditions it will not require
readjusting. The high idle is set at the factory and
cannot be adjusted. If the engine does not operate
properly and the problem appears to be fuel system
related, check the following areas before adjusting the
carburetor: Refer to MAINTENANCE section.
• Check for fuel in fuel tank
• Check fuel cap vent for blockage
• Check fuel line for pinched or obstructed areas
• Check for fuel filter blockage
• Check for a clogged air filter
If, however, the engine is hard-starting or runs roughly
or stalls at low idle speed, it may be necessary to
adjust or service the carburetor. Minor carburetor
adjustment may also be needed to compensate for
differences in fuel, temperature or altitude.
The air filter element and element cover must be
assembled to the carburetor when running the engine.
Adjust the carburetor idle fuel mixture in the order
stated as follows (Refer to Figure 17):
NOTE
Carburetor adjustments should be made only
after the engine has warmed up.
1. Start the engine and run at half throttle for 5 to 10
minutes to warm up. The engine must be warm
before making the final settings. Check that the
throttle and choke plates can fully open.
2. Idle Speed Setting: Place the throttle control into
the “idle” or “slow” position. Set the low idle speed
to 1200 rpm (± 75 rpm) by turning the low idle
speed adjusting screw in or out. Check the speed
using a tachometer (See Figure 17).
Figure 17
NOTE
The recommended low idle speed for basic
engines is 1200 rpm. To ensure best results
when setting the low idle fuel needle, the low
idle speed must not exceed 1500 rpm.
CAUTION
The tip of the low idle fuel adjusting needle is
tapered to critical dimensions. Damage to the
needle and the seat in the carburetor body will
result if the needle is forced.
3. Low Idle Fuel Needle Setting: Place the throttle
into the “idle” or “slow” position. Turn the low idle
fuel adjusting needle out (counterclockwise) slowly
from the preliminary setting until the engine speed
decreases (rich). Note the position of the needle.
Now turn the adjusting needle in (the engine
speed will initially increase) until the engine speed
decreases (lean). Note the position of the needle.
Set the adjusting needle midway between the rich
and lean settings by backing out the needle
approximately 1/8 to 1/4 turn (See Figure 18).
Figure 18
4. Recheck the idle speed using a tachometer.
Readjust the speed to the tractor specification.
LOW IDLE SPEED
ADJUSTMENT SCREW
LOW IDLE FUEL
ADJUSTMENT NEEDLE
LEAN
RICH
ADJUSTMENT
TO MIDPOINT