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 TM 55-1905-219-14-8
4-7.10A. ENGINE - MAINTENANCE INSTRUCTIONS (Continued).
ENGINE RECONDITIONING (Cont)
e. Piston - Piston Rings.
(1) To check wear, measure piston at the top level of the piston skirt (just below bottom ring) and at
right angle to the piston pin. If wear exceeds between 0.002 to 0.004 inch (0.005 to 0.010 cm), the piston must
be replaced. Also replace if there is any evidence of pitting on top of the piston.
WEAR LIMIT
0.002 to 0.004 INCH
(0.005 to 0.010 CM)
STANDARD
SERVICE LIMIT
(NEW)
(USED)
2.6744 to 2.6752 INCH
2.670 INCH
(6.7930 to 6.7950 CM)
(6.782 CM)
(2) If piston is undamaged and can be reused, remove used rings and fit new rings; never reuse rings.
After removing oil rings, break one of the oil rings in half and use this to clean carbon deposits from the ring
grooves - be careful not to scratch or enlarge grooves when doing this. Carbon removing compound, MIL-C-
19853, (NSN 6850-00-702-8451) may also be used.
(3) Before installing new rings, insert each ring into the bottom of the cylinder bore, square with piston
then check ring end gap with feeler gage.
4-394
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