LPG
Carburetor
LP-gas carburetors have three adjustment screws that
must be properly set for satisfactory operation. The
throttle stop screw controls how much the throttle plate
remains open when the throttle is pulled back
to
the
closed position. The idle adjustment screw controls the
fuel mixture when the set is operating at no load. The
main adjustment screw controls the fuel mixture when
the set is operating at full load.
No
other adjustments are
required with an LP-gas carburetor since there are no
float or choke adjustments.
Carburetor Mixture Screw Adjustments
Mixture screws should not be adjusted until the ignition
system, governor, and other fuel system components
have been checked for correct operation.
If
thecarbure-
tor is totally out of adjustment, turn the mixture screws in
until lightly seated. Fora preliminary adjustment turn the
main adjustment screw out
4
to
5
turns and the idle
adjustment screw out 2 to
3
turns.
ACAUT~ON
Forcing the mixture adjustment
Ll.3
screws tight will damage the needle
and seat. Turn in only until light tension can be felt.
Start the engine and allow it to run for about
15
minutes
at half load. Figure 6-20 shows the location of the
adjustment screws. Use the following procedure to
adjust:
1.
Stop the set and connect
a
voltmeter, frequency
meter, and load bank
to
the generator output leads.
2.
Start the generator set and apply
a
full load. Verify
that the frequency
is
within
60
f
0.5
Hz
(50
f
1
on
50
Hz
units) and adjust the governor speed adjustment
nut if necessary to obtain required frequency.
3.
Turn the main adjustment screw inward until vol-
tage or frequency drops and then outward until
voltage or frequency drops again. Set the main
adjustment screw at the point where thevoltageand
frequency are highest.
4.
Remove the load and verify that frequency
is
within
62.5
f
0.5
Hz (52
f
0.5
on
50
Hz
units). Adjust
governor speed adjustment nut
if
necessary
to
obtain required frequency.
THROllLE STOP
-
ADJUSTMENT
SCREW
SCREW
M-1878
FIGURE
6-20.
LPG
CARBURETOR ADJUSTMENTS
5.
Turn the idle adjustment screw inward until voltage
and frequency drops and engine begins to run
rough
or
starts hunting. Back out idle adjustment
screw until engine runs smoothly without hunting.
6. Pull the governor linkage toward the front of the set
so
that the throttle lever on the carburetor is resting
against the throttle stop screw. Adjust the stop
screw to obtain a setting of
55
f
1
Hz
(45
f
1
Hz
on
50
Hz
units).
7.
Release the governor linkage and observe the sta-
bility
of
the set. Set the voltage and frequency and
adjust the sensitivity of the governor as specified in
Governor
in this section. Add and remove a half load
several times
to
make certain the set does not bog
down or hunt.
Carburetor problems not corrected by mixture adjust-
ments may be caused by dirt in fuel passages
or
worn
internal parts. Under normal conditions, the carburetor
should seldom require cleaning since LP-gas vaporizes
completely before reaching the carburetor and leaves
no residue. However, a bad fuel supply may allow dirt or
oil to collect in the carburetor. This may require that the
carburetor be cleaned
to
restore satisfactory operation.
Cleaning the carburetor includes complete disassem-
bly, thorough cleaning, and replacement
of
worn parts
and gaskets.
6-20
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