Yanmar YM276 Service Manual page 124

CRANKSHAFT, MAIN BEARINGS, AND FLYWHEEL
20-15-1
DIAGNOSING MALFUNCTIONS
Scored Main Bearings (Diagnosis applies to Con-
necting Rod Bearings, also
-
See Section 10, this
Chapter)
.
Oil starvation
.
Contaminated oil
Engine parts failure
.
Excessive heat
Poor periodic service
Galled or "Wiped" Bearings
.
Fuel i n lubricating o i l (incomplete combustion)
.
Coolant i n lubrication system
.
Insufficient bearing oil clearance
.
Parts n o t lubricated prior t o engine operation
.
Wrong bearing size
Uneven Wear Pattern
.
Misaligned or bent connecting rod
Warped or bowed crankshaft
.
Distorted cylinder block
Broken Main Bearing Caps
Improper installation
.
D i r t between bearing and crankshaft journal
.
Low oil pressure
Oil pump failure
Cracked, Chipped
or
Broken Bearings
.
Overspeeding
Excessive idling
Lugging
Excissive oil clearance
Improper installation
SMEZ76011183M YM276and 276D
Kmornoro. Prinred ;n Japan