Onan MCCK - ONAN THERMO-MAGNETIC CHOKE; GOVERNOR

Beginning with Spec B, a Zenith carburetor is used.
The carburetor adjustments are the same as the orig¬
inal carburetor. The only difference is the location
of the adjustment needles (Fig. 20). The high-speed
adjustment needle A is on the bottom of carburetor.
Figure 20. Throttle Stop Screw Adjustment (Spec B and later)
To check float level, remove the entire main fuel ad¬
justment assembly from the float bowl (unscrew large
nut from float bowl (Fig. 21). The proper level from
the float to the carburetor body is 1/4”. The float
tab should just touch fuel inlet valve and not compress
the inlet valve spring. Adjust by bending the tab on
the float.
NOTE: Do not apply excessive pressure to float valve.
BEND TAB
A9i3»«* INLET VALVE SPRING
Figure 2 1. Setting Float Level
OMAN THERMO-MAGNETIC CHOKE
This choke uses a heating element and a heat-sensi¬
tive bi-metal spring to open the choke plate. The
choke solenoid, actuated during engine cranking only,
closes the choke plate according to ambient tempera¬
ture.
If adjustment is required, use the following instructions.
Bi-metal choke spring must be at ambient temperature.
Allow engine to cool at least one hour before setting.
Adjust choke by turning the choke body, which engages
a link connected to a bi-metal choke spring. Remove
flame arrestor and adapter to expose the carburetor throat.
Loosen the screw which secures the choke body. Rotate,
choke body clockwise to increase choke, and counter¬
clockwise to decrease choke action (leaner mixture).
Refer to Fig.22 for correct choke settings at various
ambient temperatures. Use drill rod or the shank of a
drill bit to measure the choke opening (Fig. 22).
GOVERNOR
The governor and vacuum booster control engine speed
(Fig. 23). Rated speed and voltage appear on the name¬
plate (also see Specifications). On a 4-pole generator,
engine speed equals frequency multiplied by 30. Thus
1800 r.p.m. gives a 60-cycle frequency and 1500 r.p.m.
equals 50-cycle frequency.
Preferred speed varies approximately 2-1/2 cycles from
no-load to full-load operation. Be sure throttle, link¬
age, and governor mechanism operate smoothly.
Linkage: The engine starts at wide open throttle. The
length of the linkage connecting the governor arm to the
throttle arm is adjusted by rotating the ball joint. Ad¬
just length so that with the engine stopped and with
tension on the governor spring, the stop screw on the
carburetor throttle lever is 1/32” from the stop pin.
This setting allows immediate control by the governor
after starting, and synchronizes travel of the governor
arm and the throttle shaft.
Speed Adjustment: With the plant operating at tempera¬
ture and no load, and with the booster external spring
disconnected, adjust the tension of the governor
spring. Turn the speed-adjusting nut to obtain a volt¬
age and speed reading within the limits shown.
Sensitivity Adjustment: Check the voltage and speed,
first with no load connected, and again with a full
load. Adjust the sensitivity to give the closest reg¬
ulation (least speed and voltage difference between no
load and full load) without causing a hunting condition.
To increase sensitivity (to get closer regulation), move
the governor spring toward the governor shaft. An ad¬
justment for too much sensitivity will cause alternate
increase and decrease of engine speed (hunting).
To decrease sensitivity, move the governor spring
toward the outer end of the governor arm. Too little
sensitivity will result in too much difference in
speed between no-load and full-load conditions.
Any change in the sensitivity adjustment usually re¬
quites a compensating speed (spang tension) adjust¬
ment,
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