Westerbeke 5.0KW BCG-60Hz Service Manual page 27

PISTONS AND CONNECTING RODS
PISTON PIN INSPECTION
Reinsert the piston pin into the piston hole with your thumb ..
You should feel a slight resistance, if the bore is misaligned·
the pin will click or bind as it enters. Try the pin from both
sides. Replace the piston if the pin can be too easily inserted
or if there is excessive play.
NOTE:
The piston pin and piston are replaced as an assembly.
Measure the outside diameter of the piston pin.
PISTON PIN 0.0.0.6300 - 0.6302in (16.001 -16.007mm)
Pistons
Check the piston surfaces for wear, seizure, cracks and
streaking. If any damage is evident, replace the piston.
Inspect the oil return hole in the oil ring groove and the oil
hole in the piston boss. Clean the piston if these are clogged.
Check the piston pin hole for signs of seizure or damage.
Replace the piston if damage is evident Measure the piston
diameter at 90° (perpendicular) to the pin bore axis.
PISTON 0.0.2.5579 - 2.55911n (64.97 - 65.00mm)
If the piston diameter is less then the standard replace
the piston.
NOTE:
The piston and piston pin are replaced as an assembly.
Piston Rings
Insert the piston ring into the cylinder bore placing it against
the top of the piston head and pressing it in. When it marks a
right angle, measure the piston ring gap with a feeler gauge.
When the gap is too large, replace the piston ring.
PISTON RING GROOVE
Standard
No.1 0.0480 • 0.04881n (1.22 ·1.24mm)
No 2 0.0476 - 0.04841n (1.21 • 1.23mm)
Oil 0.1108 -0.1116In (2.815 - 2.835mm)
PISTON RING END GAP
No.1
No.2
Oil
PISTON
Standard
0.0059· 0.01181n (0.15 - 0.30mm)
0.0138· 0.01971n (0.35 - 0.50mm)
0.008·0.028In (0.2 - 0.7mm)
limit
0.81n (0.0315mm)
0.8in (0.0315mm)
1.Oin (0.0394mm)
Check the piston ring for damage, wear, seizure and bends
replacing the rings
if
anything unusual is noted. Always
replace the piston rings when installing a new piston.
RING SIDE
CLEARANCE
FEELER GAUGE
Check the clearance between the piston ring and the ring
groove, if it exceeds the limit, replace the rings, the piston
or both.
PISTON RING SIDE CLEARANCE
Standard Limit
No.1 ring
No.2 ring
0.0012' 0.0028in (0.03 - 0.07mm) 0.00471n (0.12mm)
0.0008· 0.0024in (0.02· 0.06mm) 0.00391n (0.10mm)
Connecting Rod Bearing
Visually check the surface of the bearing. Replace those
which are lopsided, streaked or seized. When streaks or
seizure are excessive, check the crankshaft. If damage is
discovered on the crankshaft, either replace it or reuse after
undersize machining. If the connecting rod bearing indicates
severe thermal damage, replace the bearing.
Measure the inner diameter of the connecting rod bearing
and the outer diameter of the crankshaft pin. If the gap (oil
clearance) exceeds the limit, replace the bearing, and, if nec-
essary, the crankshaft...or undersize machine the crankshaft
and replace the bearings with an appropriate undersize type.
CONNECTING ROD BEARING OIL CLEARANCE
Standard Limit
0.009 - 0.00201n (0.022 - 0.052mm) 0.0041n (0.1mm)
CONNECTING ROO __ ......... ....
PISTON RING GAP
Engines & Generators
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