HYOSUNG Prima Service Manual page 49

3-21 ENGINE
PISTON PIN O.D.
Using a micrometer, measure the piston outside diame-
ter at three positions.
Micrometer(0~25 mm) : 09900 - 20201
Piston pin O.D.
PISTON RINGS
Check each ring for end gap, reading the gap with a
thickness gauge shown in the illustration. If the end gap
is found to exceed the limit, indicated below, replace it
with a new one.
The end gap of each ring is to be measured with the
ring fitted squarely into the cylinder bore and held at the
least worn part near the cylinder bottom, as shown in
the illustration.
Thickness gauge : 09900 - 20806
Piston ring clearance
(Assembly condition)
As the piston ring wears, its end gap increases reducing
engine power output because of the resultant blow by
through the enlarged gap. Here lies the importance of
using piston rings with end gaps within the limit.
Measure the piston ring free end gap to check the
spring tension.
Piston ring clearance(Free condition)
1st
2nd
Fix the piston ring in the piston ring groove, measure the
ring side clearance with the thickness gauge while
matching the sliding surfaces of piston and ring.
Piston ring-ring groove clearance
1st
2nd
Service limit 9.980 mm
Service Limit
0.75 mm
Service limit
3.2 mm
3.1 mm
Standard
0.02~0.06 mm
0.02~0.06 mm