Lycoming IO-390-D Series Maintenance Manual page 172

Crankshaft Inspection Checklist for IO-390-D Series Engines (Cont.)
Item
Examine the gear mounting
face of the crankshaft
counterbore.
If there is a hole or tang on the
crankshaft gear (instead of a
slot), examine the tang for any
nicks or dents.
Examine and measure the
alignment dowel per
instructions in the "Alignment
Dowel Inspection" in this
chapter.
Counterweight Inspection
NOTICE: A crankshaft counterweight (Figure 30) cannot be repaired. It only can be replaced.*
A counterweight roller cannot be repaired. It only can be replaced as an identical
paired set specific for each counterweight.*
*Refer to the latest revision of Service Instruction Nos. SI-1012 and SI-1535 for part numbers and
instructions to replace counterweights and rollers.
72-20
Page 146
If the mounting face of the
crankshaft counterbore is
damaged, replace the crankshaft.
If nicks or dents are found,
replace the crankshaft gear with
a new three-scallop pilot flange
gear (Figure 28).
Figure 30
Crankshaft Counterweight, Rollers, and Bushings
IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
Comments
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Findings/
Corrective Action
March 2020
Done