ADJUSTMENTS

CHECK BREAKER POINTS
Refer to Figure 18 for correct gap distances. Replace burned or faulty points. If only slightly burned dress smooth with file or fine stone. Do not use emery paper or emery cloth. Measure gap with thickness gauge gap points at .020".

Ignition breaker points, must be correctly gapped. Crank engine to fully open breaker points (1/4 turn after top center). Loosen locking screws and turn cam to adjust. Tighten breaker points and re-check gap.

Ignition points should break contact just as the 25^o timing mark aligns with the flywheel timing mark. Final timing is corrected by properly shifting the breaker point box on its mounting and using a timing light. If specified timing cannot be obtained by positioning the breaker box, make sure timing marks on gears are aligned. Timing procedures are described in the MCCK Service Manual, No. 927-550.


fig 18

CARBURETOR
The carburetor  has a high-speed main fuel adjustment (needle A) and an idle fuel adjustment (needle B). The main adjustment (needle A) affects operation under heavy load conditions Idle adjustment affects operation under light, or no load. Under normal circumstances, factory carburetor adjustments should not be disturbed. If the adjustments have been disturbed, turn needles off their seats 1 to 1-1/2 turns to permit starting, then readjust them for smooth operation.

CAUTION: Forcing the needle against its seat will damage it.
                   The needle does not completely shut off when
                    turned fully in.

Before final adjustment, allow engine to warm up. Make idle adjustment with no load connected to the generator Use a tachometer, or connect a frequency meter to generator output to observe speed or frequency. Slowly turn idle adjustment out until engine speed (or generator frequency) drops slightly below normal. Then turn needle in until speed (or frequency) returns to normal.

To set main fuel adjustments apply a full electrical load to The generator. Carefully turn main adjustment screw in until engine speed (or output frequency drops slightly below normal. Then run needle out until speed (or frequency) returns to normal. Proper carburetor adjustment cannot be assured unless the governor is properly adjusted.

Set throttle stop screw (located on carburetor throttle lever) with no load connected while running at rated speed. Turn the screw to give 1/32" clearance between the screw and pin.

Beginning with Spec B, a Zenith carburetor is used. The carburetor adjustments are the same as the original carburetor. The only difference is the location of the adjustment needles. The high-speed adjustment needle A is on the bottom of carburetor.

To check float level, remove the entire main fuel adjustment assembly from the float bowl (unscrew large nut from float bowl. The proper level from the float to the bowl flange gasket is 1/8" with full float weight on needle and spring. The float tab should just touch fuel inlet valve and not compress the inlet valve spring. Adjust by bending the tab on the float.
Do not apply excessive pressure to float valve.

fig 19

ONAN THERMO-MAGNETIC CHOKE
This choke uses a heating element and a heat-sensitive bi-metal spring to open the choke plate. The choke solenoid, actuated during engine cranking only, closes the choke plate according to ambient temperature.

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 counterclockwise 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.

GOVERNOR
The governor and vacuum booster control engine speed (Fig. 23). Rated speed and voltage appear on the nameplate (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 3 cycles from no-load to full-load operation. Be sure throttle, linkage, 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. Adjust 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 temperature 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 voltage 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 regulation (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 adjustment 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 requires a compensating speed (spring tension) adjustment.


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