be taken in the intake-to-exhaust port direction and at 20mm from the cylinder top
surface.
Unit：mm
Standard service limit
Cylinder 40.005-40.020 40.075
Piston 39.94-39.955 39.885
Cylinder to piston 0.06-0.07 0.120
Decarboning
Decarbon the piston and piston ring grooves, as illustration. After
cleaning the grooves, fit the rings and rotate them in their respective
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 the condition
will lead to reduce engine power output.
A piston whose sliding surface is badly grooved ore 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
Use a caliper gauge to measure the piston pin bore inside diameter,.
If reading exceeds the following service limit, replace it with a new one.
(Dial caliper)
Limit service: 12.30mm(0.4736in)
Piston pin outside diameter：
Use a micrometer to measure the piston outside diameter at three
positions.
(Micrometer（0-25mm）)
service limit：11.980mm(0.4717in)
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
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