Onan NHC Series Operator's/Service Manual And Parts Catalog page 308

CONNECTING RODS
Connecting rods should be serviced at the same time
as the.pistons and rings. Replaceable bushings and
bearings are used. Bearings are available in standard
or .002", .010", .020" or .030" undersize.
Proper clearance is obtained by replacing the pin
bushing and the bearings. The rod bearings are
precision size and require no reaming.
Install the connecting rods and caps with raised lines
(witness marks) aligned and with the caps facing
toward the oil base. The rod and cap numbered 2 fits
on the crankshaft journal nearest the bearing plate.
Coat the crankshaft journal bearing surfaces with oil
before installing the rods. Crank the engine by hand
to see that the rods are free. If necessary, rap the
connecting rod cap screws sharply with a soft-faced
hammer to set the rod square on the journal.
CRANKSHAFT
Inspect the bearing journals. If they are scored and
cannot be smoothed out by dressing down, the
bearing journals should be refinished to use nearest
available undersize bearings or a new crankshaft
should be installed. If a worn main bearing journal
cannot be fitted with an available precision type
undersize bearing, then refinish it to the next under-
size. If a worn rod journal cannot be fitted by installing
new bearing inserts (forged rod), then refinish it to
take the corresponding undersize bearing insert
available.
Whenever making major repairs on the engine,
always inspect the drilled passages of the crankshaft.
Clean them to remove any foreign material and to
assure proper lubrication of the connecting rods.
Crankshaft Regrinding: Crankshaft grinding requires
a trained, experienced operator, with precision equip-
ment. Onan emphasizes that if facilities or trained
personnel are not available, the crankshaft may be
sent to the factory.
Special procedures must be observed when rework-
ing crankshafts. In addition to machining, the
crankshaft must be super finished.
Shot Peening: On older model engines, shot peening
is required to prevent failures. When the shaft is
machined follow the data to shot peen each crank pin
fillet.
1. Almen gauge reading, .012-A.
2. Mask off connecting rod bearing areas.
3. Peen with .019" diameter cast steel shot.
4. Peen for 30 seconds on each crankpin fillet.
Undersize bearings and connecting rods are available
to rework the shaft to .010", .020", and .030" under-
size.
BEARINGS
Removal of the camshaft or crankshaft bearings
requires complete disassembly of the engine. Use a
press or a suitable drive plug to remove the bearings.
Support the casting to avoid distortion and avoid
damaging the bearing bore during removal and
installation. Use oil on the bearings to reduce friction
when installing and again lubricate with oil after
installing, Figure 59. Use combination bearing driver
420-0324 to install the camshaft bearings.
P R E C I S I O N T Y P B - O O N O T L I N E R E A M O R B O R E .
A L I G N H O L E IN B E A R I N G
W I T H H O L E
IN B E A R I N G B O R E
FIGURE 59. CAMSHAFT BEARING
Replacement camshaft bearings are precision type
which do not require line reaming or line boring after
installation. Coat the bearing with lubricating oil to
reduce friction. Place the bearing on the crankcase
over the bearing bore with the lubricating hole (front
only) in proper position. Be sure to start the bearing
straight. Press the front bearing in flush with the
outside end of the bearing bore. Press the rear
bearing in until past the ignition plunger hole.
New crankshaft main bearings are precision type
which do not require line reaming or line boring after
installation. They are available in standard size. .002",
.010", .020" or .030" undersize.
Before putting in the main bearings, expand the
bearing bore by placing the casting in hot water or in
an oven heater to 200° F. If practical, cool the preci-
sion bearing to shrink it.
For putting in either the front or rear main bearing,
using instructions following, always align the oil
hole(s) in the bearing with the oil hole(s) in the
bearing bore. The oil passage must be at least 1/2
open.
The cold oiled precision bearing should require only
light taps to position it.In the rearbearing plate, install
the bearing flush to 1/64 inch below the end of the
bore using combination driver (same one used for
camshaft bearing). See Figure 60.
If the special combination tool isn't available, It's necessary to
remove the lock pins with side cutters or Easy Out tool. Alter the
new bearings are installed, insert new lock pins.
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