12 / 20
WARNING
When you wash the part with gasoline or kerosene, carry out the work only outdoors or in well ventilated
area away from any source of fire to prevent a fire.
iii) Remove the carbon sticking to the combustion chamber and the exhaust port.
iv) Check the cylinder inner wall for vertical scoring. Replace the cylinder block if necessary.
v) Replace the cylinder block if you can feel scratches with a finger nail on inner wall even if there is no
overheat mark.
vi) Measure the inner diameter of the cylinder block at around 10mm from the top dead center. The
maximum limit of the inner diameter of the cylinder is φ44.070mm. Inner diameter should be measured at
four points, 0, 45, 90, 135 degrees to check roundness. The differences between the longest and the
shortest diameter should be less than 0.050mm. If the difference is more than 0.030mm, replace the
cylinder block.
vii) In case there is no defect after the above procedures i)
～
vii), the existing cylinder block can be used again,
but replace the cylinder gasket.
②
Inspection and maintenance of the pistons
i) Remove the piston pin retainers (circlips), the piston pin (wrist pin), and the piston ring from the piston. Do
not use the used piston pin retainers when you assemble the piston again.
ii) Wash the piston with gasoline or kerosene.
WARNING
When you wash the part with gasoline or kerosene, carry out the work only outdoors or in well ventilated
area away from any source of fire to prevent a fire.
iii) Remove the carbon sticking to the piston.
iv) Check the bottom surface of the piston ring groove (see Fig.7) for sticking carbon. (Fig.8) and remove the
carbon not to give damage to the piston groove.
v) Check the piston for any scratches. Replace the piston if there are scratches.
vi) Check the base surface of the piston groove for any damages with a magnifying glass. Replace the piston if
there are damages on it. (Fig.9)
vii) Measure the diameters of two
points shown in fig. 10 with a blade micrometer. The minimum limit diameter is
φ43.540mm at just below the piston groove, and φ43.980mm at below piston pin
hole (wrist pin hole).
Note 1: Measure the diameter in two directions, the direction of the piston pin
and the direction 90 degrees to the piston pin. Adopt the smaller diameter as
the data.
