IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
72-30
March 2020
Page 207
IO-390-D Series Engine Maintenance Manual
J.
Push the valve rocker shafts (Figure 15) outward and remove the rocker assemblies and
bushings.
K.
Remove the push rods and the valve stem cap from the exhaust valve.
L.
Using the shroud tube wrench (ST-142), turn each shroud tube 90º in either direction to
release the tube from the spring.
M.
Remove the shroud tubes by first releasing them from the seal seats in the cylinder head and
withdrawing the tubes.
N.
Remove the seals from the ends of the
shroud tubes. Discard the seals.
O.
Compress the valve springs with a
Valve Spring Compressor Tool (ST-
25) and remove the valve stem keys.
P.
Remove the valve spring seats and
valve springs.
Q.
Remove the cylinder base hold-down
barrel nuts (Figure 16).
Figure 16
Cylinder Hold-Down Barrel Nuts
CAUTION
AS EACH CYLINDER IS SEPARATED FROM THE CRANKCASE,
CATCH AND HOLD THE PISTON TO PREVENT IT FROM FALLING
AGAINST THE CRANKCASE AND BEING DAMAGED.
R.
Remove the cylinder from the
engine.
S.
Remove the cylinder base oil ring
from the cylinder (Figure 17) and
keep it to use as support for the
connecting rods after the pistons
are removed.
T.
Remove the valve rocker shaft
(Figure 15) from the engine
cylinder.
Figure 17
Cylinder Base Oil Ring and Cylinder Fins
