21
(2) Piston ring
➀ Replace worn out or damaged piston ring, if any.
➁ Insert a ring at a right angle to the least worn out
skirt of a cylinder, measure the clearance of ring
end gap with a thickness gauge and replace if the
end gap exceeds the service limit.
Piston ring end gap (mm)
Standard assembling
value
Service limit
Top ring
0.2 – 0.35 1.0
Second ring
0.2 – 0.35 1.0
Oil ring
0.15 – 0.35 1.0
➂ Measure the clearance between the piston ring
groove and ring and replace if the service limit is
exceeded.
➃ When the cylinder is replaced with an over size one,
use a piston ring set of over size accordingly.
Piston kit composed of piston and piston rings are
available.
Piston kit
Model Size Part code No.
S773
S.T.D.
115016990
O.S. 0.5
115016980
➄ Piston ring installing procedure
Install the piston ring to the piston as shown in the
right figure.
(3) Piston pin
Measure the outside diameter of the piston pin and
replace if the service limit is exceeded.
126V
Clearance between piston ring groove and ring (mm)
Standard assembling
value
Service limit
Top ring
0.06 – 0.1 More than 0.25
Second ring
0.05 – 0.09 More than 0.25
Oil ring
0.02 – 0.06 More than 0.15
Model Piston ring size Part code No.
S773
S.T.D.
115107240
O.S. 0.5
115107430
127V
Piston pin outside dia. (ø)
Standard assembling value Service limit
20.998 – 21.002 Less than 20.98
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