Adjustments - Onan NH Series Operator's Manual

ADJUSTMENTS
Satisfactory generating set performance relies on
correct adjustment of the carburetor, governor,
breaker points, tappets and oil pressure relief valve. If
trouble develops, follow an orderly procedure to
determine the cause before making the adjustment.
Refer to the Troubleshooting chart for help in diagnos-
ing the problem.
CARBURETOR ADJUSTMENTS
Adjust the carburetor to obtain the correct fuel-to-air
mixture for smooth, efficient operation. Perform
carburetor adjustments concurrently with governor
adjustments.
Throttle Stop: Remove all AC load. Connect a
voltmeter to the AC leads or plug the meter into one of
the unit's receptacles (if available). Hold thegovernor
arm to minimum speed and adjust the stop screw so
the voltmeter indicates 75-80 volts.
Idle Jet: Leave the voltmeter connected as for the
throttle stop adjustment. Hold the governor arm
I D L E N E E D L E
LOAD N E E D L E
T H R O T T L E
STOP SCREW
F U E L I D L E
A D J U S T M E N T
'—THIS D I S T A N C E
1 / 3 2 " A T NO L O A D
• M A I N F U E L
A D J U S T M E N T
" H I S D I S T A N C E
S H O U L D B E l / 3 2 • •
A T W I D E O P E N
T H R O T T L E
F I G U R E 29. G A S O L I N E C A R B U R E T O R
IDLE SPEED
ADJUSTMENT
SCREW
F I G U R E 30. G A S C A R B U R E T O R
against the throttle stop and turn the idle jet in until
the highest voltage is obtained. Release the governor
arm. The engine should accelerate to governed speed
and become stable.
Main Jet: Connect the AC leads to a suitable load test
panel or connect appliances obtaining a full load
condition on the generating set. With a rated load
applied, adjust the main jet to achieve the highest
voltage. Remove the connected load and hold the
governor arm to minimum speed. Release the gover-
nor arm and observe acceleration. If surging occurs at
governed speed, open the main jet slightly. However,
do not exceed one-half turn beyond the full load
point. If surging continues, adjust the governor
sensitivity.
GASEOUS CARBURETOR
When operating on gaseous fuel, follow the same
procedure given for gasoline operation except for
using the gas fuel adjustment needles. Figure 31
shows the gas carburetor with the fuel adjustment
needles and the idle speed adjustment.
Be sure to lock the choke open when operating on
gaseous fuel. If ratings of the two fuels are substan-
tially different, a readjustment of the fuel mixture is
required.
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