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IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
NOTICE: Since every counterweight has a matched pair of rollers that must stay with each
counterweight, make another non-adhesive label to identify the roller pair that
goes with each counterweight. Apply the label to the roller pair during removal
to prevent mixing the roller pairs on different counterweights during reassembly.
(2) Remove the two retaining rings (or circlips), two washers, and matched roller pair (Figure
22) from each counterweight. Discard the retaining rings and washers regardless of
condition.
Counterweight, Rollers, Counterweight Bushings, and Lug Bushings
CAUTION
NOTICE: All counterweight bushings on all of the counterweights must be replaced at the
same time.
(3) Remove the counterweight bushings in the steps below.
Tools to be used include:
• Arbor Press Spindle
• Counterweight Bushing Driver ST-92
• Counterweight Fixture Assembly ST-93
(a) Put the counterweight flat on the table, square and level against the Arbor Press
Spindle.
(b) Install the applicable Depth Control Spacer ST-93-3 or ST-93-5 (Figure 23) in the
counterweight bushing bore.
© 2020 Avco Corporation. All Rights Reserved
March 2020
Figure 22
COUNTERWEIGHT BUSHINGS MUST ALWAYS BE REPLACED
WITH NEW COUNTERWEIGHT BUSHINGS WHENEVER THESE
BUSHINGS ARE REMOVED. DAMAGE OR WEAR ON THE
CRANKSHAFT COUNTERWEIGHT BUSHINGS COULD CAUSE
FAILURE OF THE COUNTERWEIGHT AND/OR THE
CRANKSHAFT.
• Depth Control Spacer ST-93-3
• Depth Control Spacer ST-93-5
72-20
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