56.945 ÷ 56.973 mm
Fitting clearance
Top piston ring - standard coupling clearance
0.025 ÷ 0.07 mm Top piston ring - maximum clear-
ance allowed after use 0.08 mm Middle piston
ring - standard coupling clearance 0.015 - 0.06 mm
Middle piston ring - maximum clearance al-
lowed after use 0.07 mm oil scraper ring - stand-
ard coupling clearance 0.015 - 0.06 mm oil scraper
ring - maximum clearance allowed after use
0.07 mm
- Measure the diameter of the wrist pin seat on the
piston.
- Calculate the piston pin coupling clearance.
- Measure the outside diameter of the piston, per-
pendicular to the gudgeon pin axis.
- Take the measurement at 5 mm from the base in
the position shown in the figure.
- Carefully clean the seal housings.
- Measure the coupling clearance between the
sealing rings and the grooves using suitable sen-
sors, as shown in the diagram.
- If the clearance is greater than that indicated in
the table, replace the piston.
N.B.
MEASURE THE CLEARANCE BY INSERTING THE BLADE
OF THE FEELER THICKNESS GAUGE FROM THE SECOND
SEAL SIDE.
N.B.
THE PIN HOUSINGS HAVE 2 LUBRICATION CHANNELS.
FOR THIS REASON MEASUREMENT OF THE DIAMETER
MUST BE CARRIED OUT ACCORDING TO THE AXIS OF
THE PISTON.
Characteristic
Wrist pin seat on the piston: Standard diameter
15.001 ÷ 15.006 mm
Engine B 125-250
ENG - 146
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