TM 5-4310-386-14
5-43. Engine Piston and Rings (Cont).
b.
Repair.
figure 5-65).
(1)
Remove piston and rings (para. a. above).
WARNING
Dry cleaning solvent PD-680 used to clean parts is potentially dangerous to personnel and
property. Avoid repeated and prolonged skin contact. Do not use near open flame or excessive
heat. Flash point of solvent is 138°F (60 °C).
(2)
Clean all items with dry cleaning solvent, and dry thoroughly.
(3) Measure first (top) piston ring groove (1) using feeler gage. If when measured a gap S is found to exist
between inserted gage and piston, this means the axial piston clearance is within specifications and piston
is fit for further use. If gage contacts side of piston without gap, replace piston.
(4)
Measure second ring groove (2) with depth gage. Should measure .09842 inches (2.5 + 0.090 mm).
(5) Measure third ring groove (3) with depth gage. Should measure .19685 inches (5.0 + 0.030 mm).
(6)
If measurements for second or third groove is not within specifications, replace piston.
(7)
Using piston ring expander, install middle compression rings (4) and (5) and bottom oil control ring (6).
(8)
Install expander spring (7) on bottom oil control ring.
(9)
Measure axial piston ring clearance of middle compression ring using feeler gage. Should measure
.003937 to .005196 inches (.1 to .132 mm).
(10)
Measure axial piston ring clearance of bottom oil control ring using feeler gage. Should measure .00157 to
.00283 inches (0.04 to 0.072 mm).
(11)
If axial ring clearance for either ring is not within specifications, replace piston.
(12)
Using piston ring expander, remove rings from piston.
(13)
Insert three piston rings singly in cylinder and press down with piston to a distance of approximately 1.181
inches (30 mm).
(14)
Measure the gap clearance of the piston rings. Should measure as follows: top ring gap .01181 to .01771
inches (.3 to .45 mm), middle ring gap. .00787 to .01771 inches (.20 to .45 mm), and bottom ring .00984
to .01575 inches (.25 to .40 mm).
(15)
If ring gap clearances are not within specifications, replace rings.
5-180
