Onan DJA Series User Manual

GOVERNOR CUP
To remove the governor cup, remove the snap ring from
the camshaft center pin and slide the cup off. Be sure
to catch the ten flyballs that will fall out when the cup
is removed. See Figure 43.
Repair: Replace any flyballs that have flat spots or
grooves. Replace the cup if the race surface is grooved
or rough. The governor cup must be a. free spinning fit
on the camshaft center pin, but should be replaced if
excessively loose or wobbly.
Check the distance the center pin extends from the cam-
shaft gear, this distance must be 25/32-inch to give the
proper travel distance for the cup. If it is less, the
engine may race; if more, the cup will not hold the balls
properly. If the distance is too great, drive or press the
IMPORTANT: Some engines are fitted with a 0.005-inch
oversize piston at the factory. These engines are mark-
ed with an E following the engine serial number.
WHEN GOVERNOR IS
PROPERLY ASSEMBLED
THE DIMENSION SHOWN
ON DRAWING WILL BE
AS INDICATED.
CENTER PIN
SNAP RING
GOVERNOR CUP—•
GOVERNOR FLY BALL
FIGURE 43. GOVERNOR CUP
center pin in. If it is too small, replace the pin; it
cannot be removed without damaging the surface. In
some cases, if the distance is too small, the head of
the governor cup can be ground to give the necessary
7/32-inch travel distance.
Installation: To install the governor assembly, tip the
front of the unit upward. Set the flyballs in their recess-
es and position the governor cup on its shaft. Finally,
brush with heavy grease and install the snap ring on
the center pin.
PISTONS, RINGS, RODS
This engine uses a cam ground aluminum piston tapered
and fitted with three compression rings and an oil
control ring. A full floating piston pin connects the
piston to its connecting rod. The pin is held in place
with, a snap ring at each end. The lower end of the
connecting rod contains half shell, precision bearings
and the upper end', semi-finished bushings.
Removal and Disassembly:
1. Drain the crankcase oil and remove the oil base.
Remove the cylinder head.
Remove the cap from the connecting rod and push
the assembly through the top of the cylinder bore.
Replace the cap and bearing inserts in the assem-
bly.
Using a ring expander, remove the rings from the
piston.
Remove the two retaining rings and push the piston
pin from the piston.
2.
3.
4.
5.
Cylinders: The cylinder wall should be free of scratch-
es, pitting and scuffing. Check cylinder with an inside
reading micrometer for out-of-round and wear. The bore
should measure between 3.2495 inch and 3.2505 inches
and be less than 0.001-inch out-of-round.
If necessary, rebore the cylinder to fit the next avail-
able oversize piston. Pistons and rings are available in
0.005-inch, 0.010-inch, 0.020-inch, 0.030-inch and
0.040-inch oversize. If the cylinder does not need
refinishing, remove any existing ridges from the top
of the wall with a fine stone.
Pistons: Clean thoroughly and inspect the piston. Clean
the carbon from the ring grooves and be sure all oil
holes are open. If the piston is badly scored or burred,
loose in the cylinder, has badly worn ring grooves or
otherwise is not in good condition, replace it.
Check the clearance 90degrees from the axis of the
piston pin and below the oil control ring. Clearance
should be 0.0055 - 0.0075-inch. If not, replace the
piston and check the cylinder for possible recondition-
ing.
Piston Pins: The piston pin should be a thumb push
fit into the piston at room temperature. If the pin is
excessively loose, install a new one. If the condition
is not corrected, install the next oversize pin. If the
condition is not corrected, install the next oversize
pin. If the piston is worn enough that the oversize pin
will not fit, replace it.
Rings: Inspect each ring carefully for fit in the piston
grooves and seating on the cylinder wall. Fit each ring
to the cylinder wall at the bottom of its travel, using
the piston to square the ring in the bore. Check the gap
with a feeler gauge. It should be 0.010-inch to 0.020-
inch. If the gap is too small, file the butt ends of the
rings. Do not use rings that need a lot of filing, they
will not seat right on the cylinder wall. If an oversize
piston is used, use the correct oversize rings. See
Figure 44.
' 39

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English