NOTE
Do not attempt to clean the piston
skirt by glass beading, as it will
remove the tin-plating.
Inspection
If the tin-plate on the piston skirt and
the original grooves in the piston rings
are intact (no visible wear step on the
lower groove land), it is an indication of
very little wear.
scored
piston
worn or
Excessively
skirts, rings or cylinder liners may be
an indication of abnormal maintenance or
operating c o n d i t i o n s w h i c h s h o u l d b e
corrected to avoid recurrence of the fail-
The use of the correct type and
ure.
proper maintenance of the lubricating oil
filters and air cleaner will reduce to a
minimum the amount of abrasive dust and
foreign material introduced into the cyl-
i n d e r s and will reduce the rate of wear.
Long periods of operation at idle speed
and the use of improper lubricating oil or
fuel must be avoided, otherwise a heavy
Figure 11B-113. Removing or
formation of carbon may result and cause
Installing Piston Rings
the rings to stick.
Cleaning
Keep the lubricating oil and engine cool-
ant at the proper levels to prevent over-
Clean the piston components with fuel oil
h e a t i n g of the engine.
If fuel oil
and dry with compressed air.
d o e s not remove the carbon deposits, use
Examine the piston skirt and crown for
a chemical solvent that will not harm the
score marks, cracks, damaged ring
tin-plate on the piston.
groove lands or indications of overheat-
Any piston that has been severely
ing.
The piston crown, including the com-
scored or overheated must be replaced.
pression ring grooves, is not tin-plated
Indications o f o v e r h e a t i n g o r b u r n e d
and may be wire brushed to remove any
spots may be the result of an obstruction
hard carbon. Do not wire brush the pis-
i n the connecting rod oil passage.
t o n s k i r t . Clean the ring grooves with a
suitable tool or a piece of an old com-
Check the tapered fire ring groove width
pression ring that has been ground to a
in the piston crown with tool J 24599 as
b e v e l edge.
shown in Figure 11B-114 on page
11B-73. Slide the "NO-GO" wire (0.106"
Clean the inside surfaces of the piston
diameter) of the tool completely around
crown and skirt and the oil drain holes
the fire ring groove. Should the wire be
in the lower half of the piston skirt.
below flush at any one area, the piston
Exercise c a r e t o a v o i d e n l a r g i n g t h e
crown must be replaced. The "GO' wire
holes while cleaning them.
(0.100" diameter) should be flush or pro-
trude slightly from the fire ring groove.
G l a s s b e a d i n g can be used to clean a pis-
Mico Bead Glass Shot MS-M
ton crown.
Check the cylinder liner and block bore
(0.0029"-0.0058") is recommended. Al-
for excessive out-of-round, taper or
lowable air pressure is 80-100 psi
high spots which could cause failure of
(553-689 kPa). After cleaning, do not
the piston.
l e a v e glass beads in the piston crown.
