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Group 21 Engine Body
98
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Pistons
Inspecting the piston outside surfaces
Check the combustion surfaces and inside surfaces
of the pin bosses. Replace the piston if any defects
are found.
Measuring piston diameter
Measure the diameter of each piston perpendicular
(A) to the piston pin and 30 mm [1.18 in.] below the
center of the piston pin (B). If the service limit is ex-
ceeded, replace the piston. If any pistons have to be
replaced, select new pistons so that weight difference
in an engine is within assembly standards.
Piston diameter, mm [in.]
Normal value ............. Ø170 [Ø6.69]
Assembly standard ... 169.76–169.80 [6.6835–6.6850]
Service limit .............. 169.66 [6.6795]
Weight difference in an engine, g [oz]
Assembly standard ... +/- 10g [+/- 0.35 ] max.
Information stamped on top of each piston:
A – Part no.
B – Engine front side mark
C – Piston weight
Measuring piston pin diameter
Using a micrometer, measure the outside diameter of
each piston pin. If the measurement exceeds the ser-
vice limit, replace the pin.
Piston pin outside diameter, mm [in]
Nominal value ........... Ø70 [2.76]
Assembly standard ... 69.987–70.000 [2.75539–2.75590]
Service limit .............. 69.970 [2.75472]
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