Crankshaft; Bearings - Onan T260G Service Manual

CRANKSHAFT
C l e a n crankshaft thoroughly and inspect journals for
scoring, chipping, cracking, or signs of overheating. If
crankshaft has overheated, is scored, or excessively
worn, reconditioning or replacement will be required.
Examine bearing journals for cracks if overheating has
occurred.
Measure crankshaft main bearing and connecting rod
journals at several places on their diameter to check for
IN
BEARING BORE
roundness and taper.
CAMSHAFT BEARlNG
ALIGN HOLE IN BEARING
7/32"
(5.6 mm)
FROM OUTSIDE
The only recommended method of reconditioning the
crankshaft is regrinding, as required to accommodate
undersize bearings. Metallizing of bearing journals is
not recommended.
FIGURE 20. FRONT CAMSHAFT BEARING
Replacement camshaft bearings are precision type
has suitable equipment to handle precision work of this bore in the block. Before installing cam bearings use
type. Undersize main bearings are available in sizes of
Lockti@ Bearing Mount on outside diameter of bearing.
rods are available in sizes of 0.010, 0.020, 0.030 and Place the bearing on the crankcase Over the bearing
0.040 inch. bore with the lubricating hole (front only) in the proper
position. Be sure to start the bearing straight. Press in
Whenever making major repairs on the engine, always the front bearing flush with the outside end of the
inspect the drilled passages of the crankshaft. Clean bearing bore. Front cam bearing oil hole must line up
them to remove any foreign material and to assure with oiling hole in cylinder block (Figure 20). Press in
p r o p e r lubrication of the connecting rods. the rear camshaft bearing until past the ignition plunger
hole. Lubricate bearing surfaces with oil after installing.
New crankshaft main bearings are precision type which
do not require line reaming or line boring after
installation. Use a press or a suitable driver to remove
bearings. Support casting to avoid distortion and to
avoid damaging the bearing bore during removal and
installation.
If regrinding of crankshaft Journals is necessary the which do not require line reaming or line boring after
work should be done by a reputable machine shop that installation. Clean outside of the bearing and bearing
0.010, 0.020, and 0.030 inch. Undersize connecting Use a combination bearing driver to install bearings.
BEARINGS
With camshaft and crankshaft removed, use a micro-
meter to measure diameter of bearing journals. Use a
dial bore gauge or a telescopic gauge and micrometer
to measure inside diameter of bearings. Refer to
DlMENSlON AND CLEARANCE to determine if clear-
ances are within specifications.
Any bearing that is scored, chipped, pitted or worn
beyond the specified limits must be replaced.
Removal of the camshaft bearings requires complete
disassembly of the engine: Use a press or a suitable
driver to remove bearings. Support casting to avoid
and to avoid damaging the bearing bore
during removal and installation.
Before installing main bearings, expand bearing bore by
placing' the casting in an oven heated to 2 0 0 F (94°C). If
practical, cool the precision bearing to shrink
it.
Before installing the front main bearing, use the towelette
included with the bearing kit to clean the outside of the
bearing and bearing bore in the block.
Breathing vapor from towelette and
CAUTION
prolonged contact with skin can be
harmful.
Be
sure area is well ventilated.
After allowing three to four minutes for drying, apply the
Locktite from the small tube to the mating surfaces of the
bearing and the bearing bore. Align the oil holes in the
bearing with the oil holes in the bearing bore (Figure 22).
The oil passage should be at least half open. Install the
bearing flush with the block, using the combination
driver. Wipe off excess Locktite around the bearing.
Allow at least one hour for hardening at room
temperature.
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