HYOSUNG WOW90 Service Manual page 51

3-23 ENGINE
◉ PISTON PIN O.D.
Using a micrometer, measure the piston pin outside
diameter at three positions.
Piston pin O.D.
Micrometer(0~25mm) : 09900 - 20201
◉ PISTON RINGS
Check each ring for the clearance, reading the clear-
ance with a thickness gauge shown in the illustration. If
the clearance is found to exceed the limit, indicated
below, replace it with a new one.
The clearance 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.
Piston ring clearance
(Assembly condition)
Thickness gauge : 09900 - 20806
As the piston ring wears, its clearance increases reduc-
ing engine power output because of the resultant blow
by through the enlarged clearance. Here lies the impor-
tance of using piston rings with the clearance within the
limit.
Measure the piston ring free clearance to check the
spring tension.
Piston ring clearance
(Free condition)
Service limit
11.980 mm (0.472 in)
Service limit
0.75 mm (0.030 in)
Service limit
3.6 mm (0.142 in)