TM 5-3825-229-14&P
6-11. PISTONS AND CONNECTING RODS (cont)
c.
Cleaning and Inspection (cont).
(1) Remove dirt and deposits from piston surfaces with a cleaning solvent (PD-680). Clean piston ring grooves with
a groove cleaner. Do not remove metal from the ring groove sides.
(2) Check piston for scoring, damaged ring grooves and signs of overheating. Inspect pistons for cracks and bent
or broken ring lands. Replace any piston that is badly scored or burred, cracked, has badly worn ring grooves
or is not in good condition.
(3) Check piston ring clearance.
(a)
Check ring end gap by inserting each ring into cylinder in the location it is to be used. Use a piston to push
ring squarely down in cylinder bore far enough to be in the ring travel area. Check ring end gap with a feeler
gauge. Ring gaps must be as shown below:
Ring
Gap
Top Ring
MIN: 0.014 inch (0.35 mm)
MAX: 0.024 inch (0.60 mm)
Intermediate Ring
MIN: 0.010 inch (0.25 mm)
MAX: 0.024 inch (0.60 mm)
Oil Control Ring
MIN: 0.010 inch (0.25 mm)
MAX: 0.020 inch (0.50 mm)
(b)
If ring end gap does not meet specifications, check for the correct set of rings and correct bore size. A
cylinder bore that is 0.0012 in. (0.03 mm) undersize will reduce the end gap 0.0031 in. (0.08 mm).
6-24
