KYMCO Downtown 350i Repair Manual page 218

4.Engine
Measure the outside diameter of the piston at 9 mm up from the bottom of the
skirt at a 90° angle to the piston pin. Measure the piston with vernier calipers or a
micrometer. Check the piston for wear, damage, and extreme discoloration.
Subtract the diameter of the piston from the maximum front to rear diameter
measurement of the cylinder to calculate the piston-to-cylinder clearance.
Replace the piston and cylinder as needed to achieve a correct piston-to-cylinder
clearance.
Item
Piston-to-cylinder clearance
Measure the piston pin diameter with a micrometer. Measure the piston pin bore
diameter with vernier calipers or a small bore gauge. Measure at three different
points for each. Replace the parts if any of the specifications are not met.
Item
Piston pin hole I.D.
Piston pin O.D.
Piston-to-piston pin clearance
Downtown 350i
Standard (mm)
0.010 - 0.030
Standard (mm)
15.002 - 15.008
14.994 - 15.000
0.002 - 0.014
4-44