HYOSUNG Sense SD-50 Service Manual page 40

As a result of the above measurement, if the piston-to-cylinder
clearance exceeds the following limit, overhaul the cylinder and use
an oversize piston, or replace both cylinder and piston. The mea-
surement for the bore diameter should be taken in the intake-to-
exhaust port direction and at 20mm from the cylinder top surface.
Cylinder
Piston
Cylinder to piston
DE-CARBONING
De-carbon the piston and piston ring grooves, as illustrated. After
cleaning the grooves, fit the rings and rotate them in their respec-
tive grooves to be sure that they move smoothly.
Carbon in groove is liable to cause the piston ring to get stuck in
the groove, and this condition will lead to reduced engine power
output.
A piston whose sliding surface is badly grooved or scuffed due to
overheating must be replaced. Shallow grooves or minor scuff can
be removed by grinding with emery paper of about # 400.
PISTON PIN BORE
Using a caliper gauge, measure the piston pin bore inside diameter.
If reading exceeds the following service limit, replace it with a new
one.
09900-20605
Service limit
PISTON PIN O.D.
Using a micrometer, measure the piston outside diameter at three
positions.
09900-20205
Service limit
STD Service Limit
41.005-41.020
40.935-40.950
0.065-0.075
Dial calipers
10.036 mm(0.4079 in)
Micremeter(0-25 mm)
9.980 mm(0.3929 in)
Unit: mm
41.070
40.885
0.120
ENGINE 3-18