Westerbeke 20B TWO Tehnical Manual page 57

Cylinder Block Inspection
Inspect the cylinder block. If it is found defective, repair or replace the block.
Cylinder Bore (mm):
Mgdel
20B
30B
Standard
76
+
0.03 -0.0
76
+
0.03 -0.0
Wear Umit Before Rebore:
+
0.02 mm
Cylinder Reboring
When reboring a cylinder, use the following procedure.
1. Select a piston size: 0.25
as
or 0.50
as.
2. Measure the piston diameter.
3. Reboring finish dimension
=
[piston
00]
+
[clearance] - [honing allowance (0.2 mm)]
Clearance (between piston and cylinder)
Standard: 0.071 - 0.084 mm (A-D)
CAUTION
A ox.10mm ppr
from upper end
C enter
Front
~
~\J7
,
L -
'--
ower
Measuring position
Cylinder Bore Measuring Positions
Direction of
measuing
I~
55
l
mm
0
Measure
diameter
here
----L.-~r
Measuring Piston Diameter
When it is necessary for a cylinder to be rebored to the next over size, the remainders must
also be rebored to the same over size.
55
Westerbeke Engines