Piston/Piston Ring - Westerbeke W70GA Service Manual

PISTON-PISTON RING
INSPECTION
I
REPAIR
PISTON
1. Inspect the outer circumferences of all pistons for
seizure or scoring. Replace if necessary.
2. Measure the outer diameter of each piston at a right
angle (90°) to the piston pin, 18 mm (0.709
in)
below
the oil ring land lower edge;
STANDARD VALUE: 85.944 • 85.964mm (3.3836 • 3.3844in)
0.25mm OVERSIZE: 86.194 - 86.214mm (3.3935 - 3.3942in)
D.50mm OVERSIZE: 86.444 • 86.464mm (3.4033 • 3.4041in)
18mm·
(D.709in
PISTON
INSPECT FOR WEAR,
SCORING, CRACKS,
OVERHEATING AND
EXCESSIVE WIDENING
~~§§~~~'OF
RING GROOVES
5. inspect the piston rings for damage, abnormal wear, or
breakage. Replace if necessary.
6. Insert the piston ring into the cylinder by hand and push
it to the bottom of the ring travel by using the piston.
7. Measure the ring end gap.
END GAP TOP: D.20-0.35mm (O.D08-0.014in)
SECOND: D.15·D.3Dmrri (O.OD6-D.012in)
OIL RING: D.20-0.7Dmm (D.008-0.028in)
MAXIMUM: 1.Dmm (0.039in)
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INVERTED
PISTON
:
~CYLINDER
·a
PISTON RING .
3. Check the piston to cylinder clearance.
CLEARANCE: 0:036-0.075 (D.D014-0.003Din)
MAXIMUM: 0.15mm (D.DD59in)
4. If the clearance exceeds the maximum, replace the
piston or rebore the cylinders to fit oversize pistons.
NOTE: If
the piston is replaced, replace the piston rings
also.
PISTON;
CLEARANCE.
I I
I '
8. Measure the piston ring to ring cleai:ance around the
entire circumference using a new piston ring.
CLEARANCE TOP: D.03-D.07mm (O.DD1-0.003in)
SECOND: D.03-D.07mm (D.001-0.0031n)
MAXIMUM:
D.15mm (Q.DD6in)
NOTE:
Measure the clearance around the entire
circumference ofthe ring,groove.
NOTE: If
replacing piston rings check the piston ring
gaps. New rings are packaged with detailed instructions
that often supersede the service manual.
Engines & Generators
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