Counterweight Removal - Lycoming IO-390-D Series Maintenance Manual

NOTICE: Skip the next step if a constant speed propeller is used because an expansion plug is
not installed in the crankshaft.
CAUTION
C. If installed, remove the larger expansion plug and inner plug (Figure 21) from the crankshaft
by punching a 1/8 in. (3.175 mm) to 3/16 in. (4.763 mm) hole in the center of the plug. Use a
hook or bent rod to pull out the plug. Remove any little pieces of plug remnants. Discard the
expansion plug and inner plug.
CAUTION
NOTICE: Counterweights (Figure 22) of a specific order are installed in specified locations
identified in the latest revision of Service Instruction No. SI-1012.
During counterweight removal, identify the counterweight and its location on a non-
adhesive label and temporarily apply this label to the counterweight for reference on
reassembly.
D. Counterweight Removal
(1) Remove each counterweight from the crankshaft. Apply the non-adhesive label to
identify the location and position on the crankshaft for reference on reassembly
72-20
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DO NOT DRILL THE EXPANSION PLUG OR USE A MAGNET TO
REMOVE THE PLUG OR ANY LITTLE PIECES OF PLUG REMNANTS.
Crankshaft and Counterweight Assembly
WHEN TOUCHING COUNTERWEIGHTS AND ROLLERS DO NOT
MAKE SCORES, SCRATCHES, OR ETCH MARKINGS OF ANY KIND
ON THE CRANKSHAFT AND ROLLERS. A MARK IN ANY OF THESE
AREAS CAN CAUSE THE PART TO WEAKEN AND POSSIBLY FAIL.
IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
Figure 21
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March 2020