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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 250i-R= 77.950±0.005 mm
Piston 300i-R= 83.950±0.005 mm
Ring groove / piston ring:
• Using a feeler gauge measure the
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.
Piston pin diameter
15.997-16.000 mm
Piston pin hole diameter in the piston
16.004-16.009 mm
Connecting rod hole diameter
16.000-16.011 mm
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