POWERHEAD - 4-1590-826148R2 MARCH 1997
Connecting Rods
1. Check connecting rods for alignment by placing
rodsonasurfaceplate.Iflightcanbe seenunder
any portion of machined surfaces, if rod has a
slightwobbleonplate,orifa0.002in.(0.051mm)
feeler gauge can be inserted between any
machined surface and surface plate, rod is bent
and must be discarded.
2. Overheating: Overheating is visible as a bluish
bearing surface color that is caused by
inadequate lubrication or excessive RPM.
3. Rust: Rust formation on bearing surfaces
causes uneven pitting of surface(s).
51853
a
a - Pitting
4. Water Marks: When bearing surfaces are
subjected to water contamination, a bearing
surface“etching”occurs.Thisetchingresembles
the size of the bearing.
51853
5. Spalling: Spalling is the loss of bearing surface,
and it resembles flaking or chipping. Spalling will
be most evident on the thrust portion of the
connecting rod in line with the “I” beam. General
bearingsurfacedeteriorationcouldbecausedby
or accelerated by improper lubrication.
51853
a
a - Spalling
6. Chatter Marks: Chatter marksare the resultofa
combination of low speed - low load - cold water
temperature operation, aggravated by
inadequate lubrication and/or improper fuel.
Under these conditions, the crankshaft journalis
hammered by the connecting rod. As ignition
occurs in the cylinder, the piston pushes the
connecting rod with tremendous force, and this
forceis transferredto the connecting rod journal.
Since there is little or no load on the crankshaft,
it bounces away from the connecting rod. The
crankshaft then remains immobile for a split
second until the piston travel causes the
connecting rod to catch up to the waiting
crankshaft journal, then hammers it. The
repetition of this action causes a rough bearing
surface(s) which resembles a tiny washboard.In
some instances, the connecting rod crank pin
borebecomes highlypolished.During operation,
theenginewill emita “whirr” and/or“chirp”sound
when it is accelerated rapidly from idle speed to
approximately 1500 RPM, then quickly returned
to idle. If the preceding conditions are found,
replace both the crankshaft and connecting
rod(s).
51853
a
a - Chatter Marks Between Arrows
To Next Page
Loading...
Need help?
General
