SECTION 2 - PROCEDURES
2-24 3121801
2.15 AUTOMATIC CHOKE - FIELD ADJUSTMENT
(DF-750)
Inspection
NOTE: All automatic choke assemblies have been pre-set to oper-
ate between -7°C and 38°C (20°F and 100°F) with little or
no adjustment. If the machine will be operated for prolong
use outside these temperature ranges, adjustments could
be made to improve performance of the engine.
The machine will take time to warm up and you may expe-
rience low power or rough running for the first few minutes
of operation or until the engine warms up. LET THE ENGINE
WARM UP.
Make sure that the choke shaft operates freely and does not
bind. this can be done without removing the air horn by rotat-
ing the bronze coupling with an eraser on a pencil or by
removing the vacuum pull off line at the manifold and supply
a small amount of vacuum to the hose. the choke rod should
move freely using either method.
Adjustments
NOTE: If the choke rod is binding make sure the support bracket is
straight.
1. There are two adjustments Vertical (loosening the air
horn nuts) and Horizontal (loosening the bracket to
adaptor screws). These two adjustments should resolve
any binding problem.
2. To adjust the choke at 21°C (70°F) ambient, remove the
air horn and reinstall the nut that holds the choke and
support bracket securely making sure the choke moves
freely.
3. Loosen the 3 top cover screws and rotate the top cover
till the choke butterfly is closed with 1/32 in space
between the plate and the wall of the carburetor.
4. If the ambient temperature is less then 21°C (70°F) the
top cover counter should be rotated CCW 1 mark for
every -15°C (5°F) less then 21° C (70°F).
5. If the ambient temperature is more then 21°C (70°F) the
top cover counter should be rotated CW 1 mark for
every -15°C (5°F) less then 21°C (70°F)
.
Reassembly
Reassemble the air horn making sure the choke is not binding,
test to insure that none of the settings have moved and the
choke is not binding.
The vacuum pull off should be set such that when vacuum is
applied to the choke system the choke butterfly is full open.
NOTE: If the machine starts and stalls immediately or if it is
extremely cold, limiting the choke pull off to 75% to 90%
may improve the performance of the machine. No adjust-
ment is normally required.
Diesel Engine
NOTE: Never run the fuel tank dry. Diesel engines cannot be
restarted after running out of fuel until the fuel system has
been air-vented or ‘bled’ of air. See the Kubota Instruction
Manual for the proper procedure.
Figure 2-22. Automatic Choke Adjustment (DF-750)
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