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YO-233-B2A Engine Maintenance Manual
TEO-540-A1A Engine Maintenance Manual
NOTICE: Always install a larger 0.010 in. oversized Heli-Coil
the cylinder head to replace a standard sized Heli-Coil
sized Heli-Coil
Heli-Coil
shown Figure 57.
(1) Disable all power to the engine to prevent propeller rotation and engine start. Disconnect
ignition leads from all spark plugs.
(2) If not already done, remove the Heli-Coil
(a) Insert the T-shaped Removing Tool
P/N 64595 (Figure 58) in the spark
plug hole. Press the tool down
firmly for the edge of the tool to cut
into the top thread of the insert.
(b) Turn the tool counterclockwise to
the remove the insert.
(3) Examine the removed Heli-Coil
the removed Heli-Coil
(4) Apply of coat of grease liberally to the Bottom Tap 64596-1 (Figure 59).
(5) If the Heli-Coil
precautions to prevent metal shavings from falling into the combustion chamber.
CAUTION IF METAL SHAVINGS FALL INTO THE COMBUSTION CHAMBER
(6) Turn the crankshaft to the start of the compression stroke.
(7) Put 8 ft. (2.4 m) of 3/8 in. (9.5 mm) nylon rope through the opposite spark plug hole.
(8) Turn the crankshaft to force the rope against the bottom of the spark plug hole that is to
be tapped.
(9) Use the 0.010 in. oversized Bottom Tap 64596-1 (Figure 59), to tap an oversize hole for
the new 0.010 in. oversized Heli-Coil
(10) Remove all chips and shavings to prevent contamination from foreign object debris.
(11) Remove the rope from the spark plug hole.
0.010-Inch Bottom Tap 64596-1
© 2021 Avco Corporation. All Rights Reserved
February 2021
®
insert with another standard sized Heli-Coil
®
inserts are identified by three marks on the tang of the Heli-Coil
®
®
is 0.010 in. oversized, replace the cylinder.
®
insert is replaced while the cylinder is installed on the engine, take
OF THE CYLINDER, STOP AND REMOVE ALL SHAVINGS AND
DEBRIS. THE COMBUSTION CHAMBER MUST BE CLEAN
WITHOUT DEBRIS.
Figure 59
®
®
insert from the spark plug hole as follows:
Removing Tool P/N 64595
to make sure it is not 0.010 in. oversized (Figure 57). If
®
insert.
Inserting Tool P/N 64594
insert in the spark plug hole on
®
insert. Never replace a standard
®
insert. The oversize
®
Figure 58
Figure 60
insert as
72-30
Page 145
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