Westerbeke 5.0KW BCG-60Hz Service Manual page 38

CYLINDER BLOCK INSPECTION AND PISTON CLEARANCE
NUMBERS INDICATE THE
SUGGESTED ORDER OF
DISASSEMBLY
CYLINDER
BLOCK
1 OllU'EH
PlUG
1/4'~
2
D O W E l - - - - . o •
6STUDS8X5D-7T/ .
8
KNOCK BUSHINGS 6 X
9~
CYLINDER BLOCK INSPECTION
1. Before inspecting, clean the cylinder block to ensure that
the water and oil holes are not plugged. If clogged, clear
with compressed
air.
2. Check for cracks and damage. Use a flaw detecting com-
pound as needed. Replace the block if defective.
3. Inspect the mating surface. Using a straight edge and
feeler gauge measure the flatness of the top surface.
Grind or replace if the limit is exceeded.
FLATNESS STANDARD VALUE: 0.0020 in (0.05 mm)
LIMIT: 0.DD4 in (0.1 mm)
4. Inspect the cylinder bore. Using a cylinder gauge, mea-
sure the bore at six places (as shown in the diagram).
Calculate the difference between the max. and min. val-
ues. If worn or damaged, rebore or replace the cylinder.
CYLINDRICITY STANDARD VALUE: 0.0004 in (0.01 mm) or less
CYLINDER BORE: 2.5591 - 2.5602 in (65.00 - 65.03 mm)
0.47 IN [12rnrn) DOWN
UPPER
CENTER
MEASURING
lOWER
DIRECTION MEASURING POSITION
CHECKING THE PISTON CLEARANCE
Calculate the difference between the minimum cylinder bore
in the thrust directitm and the piston outer diameter shown in
. the illustration. If the difference exceeds the specified range,
replace the piston or cylinder block, or rebore the cylinder.
PISTON TO CYLINDER CLEARANCE STANDARD:
0.0008 - 0.0016 In (0.0 - 0.04
0101)
BORING THE CYLINDER
1. Select an oversize piston based on the cylinder with the
maximum bore and maximum damage depth.
2. Using the outer diameter (at the specified measurement
point) of the selected oversize piston, calculate the boring .
dimension.
Boring dimension
=
(Piston D.O.)
+
(piston clearance) - (honing margin: 0.0008i" (0.02mm))
OVERSIZE PISTON OUTSIDE DIAMETER AND CYLINDER
(INNER DIAMETER FINISH DIMENSION (REF))
Size
Mark
Piston Dia.
Cylinder loner Dia.
0.250.S. 25 2.5677 - 2.568910 2.5693 - 2.56971n
(65.22 - 65.25mm)
(65.26· 65.27mm)
0.500.S. 50 2.5776 - 2.5787in 2.5791 ·2.5795in
(65.47 - 65.50mm) (65.51 - 65.52mm)
0.750.S. 75 2.5874 - 2.58861n 2.5890 • 2.5894in
(65.72 - 65.75mm) (65.76 - 65.77mm)
1.000.S. 100 2.5972 - 2.59841n 2.5988 - 2.5992in
(65.97 - 66.o0m) (66.01 - 66.02mm)
3. Bore the cylinder to obtain the calculated dimensions.
4. Hone to finish the cylinder inner diameter.
S. Check again for cylindricity and piston clearance .
Engines & Generators
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