Fig. 31 - Checking piston ring end gap
Fig. 32 - Checking clearance between piston
rings and piston ring grooves in piston.
Fig. 33 - Correct assembly of piston rings.
Cleaning pistons
Descale piston crown and piston ring grooves using an emery
cloth.
Remove any buildups from gudgeon snap ring seats.
After all parts have been thoroughly cleaned and before further
checking is performed, examine them carefully for cracking or
damage which may require replacement.
Light scoring o seizing signs can be removed with very fine emery
cloth.
Checking pistons
Measure piston diameter with a micrometer gauge as shown in
figure 28.
If the diameter measured is below the specifications given in table
on page 35, the piston needs to be replaced.
Checking gudgeon pin and gudgeon pin seat in
piston
If either gudgeon or related seat diameter measurement differs
from specifications, the replacement of the worn-out part is recom-
mended.
Check also gudgeon pin snap rings for proper elasticity or da-
mage. If they are found not conforming to the operating conditions
replace them.
Checking piston ring end gap
Both the compression ring and the oil control ring ends installed
in the cylinder should not have a gap exceeding the specifications
shown in table.
This check is carried out by inserting the piston rings into the
cylinder so as the ring end gap can be measured with no.
5.9030.270.0 special thickness gauge, as shown in figure 31.
NOTE - Excessive clearance between piston rings and piston ring
grooves in piston may cause high lubricant consumption as well
as engine power loss.
Piston rings must be replaced each time piston is removed or
cylinders are replaced.
engine
crankshaft
12
1
38
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