Aeon AT56-69E, Service Manual, Page: 81 / 196

ENGINE
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5. Measure connecting rod small end ID. Replace crankshaft if
out of round.
6. Measure piston ring to groove clearance by placing the ring
in the ring land and measuring with a thickness gauge. Replace
piston and rings if ring-to-groove clearance exceeds service
limits.
RING TO GROOVE CLEARANCE
Top Ring
Std: 0.02--0.06 mm
Limit: 0.1 mm
Second Ring
Std: 0.02--0.06 mm
Limit: 0.1 mm
Oil Ring
Std: 0.022-0.08 mm
Limit: 0.12 mm
PISTON RING INSTALLED GAP
1. Place each piston ring inside cylinder using piston to push
ring squarely into place as shown.
PISTON RING INSTALLED GAP
Top Ring
Std: 0.1--0.3 mm
Limit: 0.8 mm
Second Ring
Std: 0.35--0.5 mm
Limit: 1.0 mm
Oil Ring
Std: 0.2-0.7 mm
Limit: 1.5 mm
2. Measure the gap with a feeler gauge at both the top and
bottom of the cylinder.
NOTE: Measure at two points in the cylinder
A difference in end gap indicates cylinder taper.
The cylinder should be measured for excessive taper
and out of round.
3. If the installed gap measurement exceeds the limit, replace
the rings. If using new rings and the measurement is too small,
file the ring ends to achieve the proper gap.
NOTE: Always check piston ring installed gap after
re-boring a cylinder or when installing new rings. A
re-bored cylinder should always be scrubbed
thoroughly with hot soapy water, rinsed, and dried
completely. Wipe cylinder bore with an oil rag
immediately to remove residue and prevent rust.