Piston Wear; Ring Groove / Piston Ring; Ring End Gap; Inspect The Connecting Rod, The Piston Pin And The Piston For Wear - SHERCO 250 SEF-R Workshop Manual

Piston wear

 Using a micrometer measure the outside
diameter of the piston [A] 10mm [B] above
the bottom of the piston and at right angles
to the axis of the piston.
If the outer diameter of the piston is below
the tolerance it must be replaced.
Piston 250 SEF-R= 75.950±0.005 mm
Piston 300 SEF-R= 83.950±0.005 mm

Ring groove / piston ring

 Using
a feeler
clearance between the piston ring and the
ring groove.
 Check in several places to determine the
actual clearance if the clearance is greater
than the maximum, replace the piston ring
and if necessary the piston.
Ring groove / piston ring
Standard
Compression ring: 0.030-0.065 mm
Limit 0.13 mm
Oil control ring: 0.020-0.055 mm
Limit 0.13 mm

Ring end gap

Compression ring : 0.3-0.4 Limit 0.7 mm
Oil control ring : 0.3-0.5 mm
Inspect the connecting rod, the
piston pin and the piston for wear
 Visually inspect the circlips in place.
If they appear worn or distorted replace
them. If the hole for the circlips appears
worn replace the piston.
 Measure the piston pin with a micrometer.
If at any place on the pin the diameter is
below the limit replace the piston pin.
 Measure the diameter of the piston pin
holes in the piston and the hole in the
connecting rod. If the one or more holes in
the piston are incorrect replace the piston.
If the diameter of the hole in the connecting
rod is incorrect, replace the connecting rod.
gauge measure the
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