Valves And Springs; Rocker Arms; Cylinders - Kohler KD 425-2 Workshop Manual

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KD 425-2 Workshop Manual_cod. ED0053029360_1° ed_ rev. 00

Valves and springs

In order to check the springs for possible failure measure the lengths
under load as shown in figure 16.
The permissible tolerance for loads and lengths is ± 10%. If the fi-
gures measured do not fall within these values, the springs must be
renewed.

Rocker arms

Make sure that the facing surfaces between rocker and pin are not
scored and show no signs of seizure. If such marks are encountered,
renew rocker and pin. Rocker / pin clearance (fig.17):
Fitting mm
0,03 ÷ 0,06
Rocker axial play (fig.17):
Fitting mm
0,05 ÷ 0,130
Make sure that the rocker arm adjusting screw is not worn and that
the lubrication hole is free of dirt.

Cylinders

Air cooled with cylinder barrels in special cast iron with integral liners.
Use a dial gauge to check internal diameters (C-D) at three different
heights (fig.18).
Maximum permitted taper (A-B) and ovality (C-D) is 0.06mm.
Diameter of cylinders (fig.18):
KD 425-2
If the diameter of the cylinder does not exceed said values or if there
are slight surface scores on the cylinder, it will be sufficient to change
the piston rings.
Do not manually hone the cylinder bore surfaces with eme-
ry cloth or other means.
The cross-hatch pattern should be at an angle of 90°÷120°; lines
should be uniform and clear in both directions.
Average roughness must range between 0.5 mm 1 µm.
The cylinder surface which comes into contact with piston rings
should be machined with the plateau method.
If the taper and ovality of the cylinder exceed the values indicated,
then the cylinder and piston must be renewed.
CHECKS AND OVERHAUL
Max. wear mm
0,15
Max. wear mm
0,5
Ø 85 ÷ 85,015
X
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