Westerbeke W-46 - Page 23

INSPECTION/REPAIR
3. Replacing pistons.
Replace the piston with a new
one if the measurement exceeds
the service limit. When any
pistons have to be replaced,
the variance in weight among
the pistons must not exceed the
limit. It is recommended that
the cylinder number be stamped
on the piston selected for use
in a particular cylinder for
convenient identification.
When the cylinder sleeves are
bored to the oversize, the
pistons and piston rings of the
same oversize dimension should
be used. There are two over-
sizes for pistons and piston
rings: +0.25 mm(0.00984in.) and
+ o.somm (0.01969 in.). The
variance in weight among the
pistons per engine should be ~3
grams (~O.loz) max.
4. Piston ring gaps.
Always check piston r ~ng gaps
before assembling r1ngs on
piston. Insert rings into the
cylinder squarely by using a
piston. Check gaps with feeler
gauge.
Fron't .of engine
t
Piston weight
Piston weight marking
/
Piston ring
Checking piston ring gap
Specifications
Unit· mm (in )
Item
Piston ring gap
s. Piston ring grooves.
Insert the compression and oil
rings of known thicknesses into
the grooves; measure the side
clearance with a feeler gauge
(A) •
Standard
0.30 ~o.5o
(0.0118 -0.0197)
Service
limit
1.5
(0.059)
Specifications
Unit· mm (in l
Item
Standard
Repair
limit
No.
1 compression
0.050-0.080 0.20
Fit in ring
ring
(0.00197- 0.00315)
(0.0079)
grooves
No. 2 compression ring
O.Q25 - 0.060
0.15
Oil ring
(0.00098 - 0.00236) (0.0059)
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