TM 9-4940-549-14&P
Cleaning, Inspection, and Repair.
c.
(1) Thoroughly clean the air heads by brushing or scraping lightly
to remove accumulations of carbon deposits, being careful not to
damage gasket surfaces. Be sure the gasket surface is free of
all gasket particles.
(2) Use solvent and wash away all accumulated oil. Be sure bore
of cylinder is clean, and that all gasket particles are removed
from surfaces.
(3) Wash pistons in solvent and remove all accumulated oil or car-
bon. Pay particular attention to the ring grooves. Be sure
that oil return holes in the oil control wiper ring grooves are
open, and that grooves themselves are absolutely clean.
(4) Inspect the cylinder bore for any signs of scoring or scuffing.
If the cylinder bore shows signs of wear or scoring, as indi-
cated by visible ridging at the end of ring travel, it must be
replaced (see paragraph (6) ).
(5) Inspect the piston for signs of scoring, or for any indication of
cracked or broken lands. If these signs are found, replace the
piston. If piston shows no signs of scoring, or cracked or
broken lands, check the condition of ring grooves for signs of
excessive wear. A tapered ring groove would result in exces-
sive clearance, and that piston should be replaced.
If new ring sets are to be installed
on the pistons, and the old cylinder
is going to be reused, the cylinder
walls must be deglazed, or slightly
roughened to provide a proper seat-
ing-in surface for the new piston
rings.
(6) Cylinders that passed inspection in paragraph (4), and are to
be reused, must be deglazed as follows:
(a) Use a No. 80 grit abrasive cloth (NSN 5350-00-192-5047) dampened
in petroleum spirits, or solvent, and move it over the surface
of the bore in a rotating and reciprocating motion with a very
light pressure.
(b) After deglazing, the cylinder wall should be thoroughly
cleaned with a hot soapy solution, using a good stiff
bristle (not wire) brush. Rinse thoroughly with hot water
then check cleanliness of the bore by wiping with a soft
white paper cloth. If the paper shows more than a slight
discoloring, the cylinder has not been properly cleaned.
14-16
