Onan DJA Series User Manual

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' con-
necting 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. • ^ -
Important: Some engines are fitted with a .005" oversize
piston at the factory. These engines are marked with an E
following the engine serial number.
REMOVAL AND DISASSEMBLY
1. Drain the crankcase oil and remove the oil base.
2. Remove the cylinder head.
3. 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 assembly.
4. Using a ring expander, remove the rings . from the
piston.
5. Remove the two retaining rings and push the piston pin
from the piston.
CYLINDERS
The cylinder wall should be free of scratches, pitting and
COMPRESSION RU GS
*- OIL CONTROL RING
RAIL
3^
HEAVIEST COMPRESSION
RING IN TOP GROOVE
•RAIL
•EXPANDER
FIG. 12-1
scuffing. Check cylinder with an inside reading micrometer
for out-of-round and wear. The bore should measure between
3:2495" and 3.2505" and be less than .001" out-of-round.
If necessary, rebore the cylinder to fit the next available
oversize piston. Pistons and rings are available in .005",
.010", .020", .030" and .040" 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 \rorn ring grooves or otherwise is not in good
condition, replace it.
Check the clearance 90° from the axis of the piston pin and
below the oil control ring. Clearance should be .0055 -
.0075". If not. replace the piston and check the cylinder
for possible reconditioning.
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 piston is wom enough that the oversize
pin will not fit, replace it.
RINGS
Inspect each ring carefully for fit in the piston grooves and
33
CONNECTING ROD
BUSHINGS-
BUSHING ENDS MUST
BE FLUSH WITH SIDES
OF ROD TO PERMIT
1/16" OIL GROOVE
BETWEEN BUSHINGS
PRECISION TYPE
BEARING
CROSS-SECTION
MEASURE CLEARANCE IN
DIRECTION INDICATED BY
ARROW
AS8I
FIG. 12-2

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English