單項選擇題

A.poor cooling of cylinder walls
B.improper cooling of the piston
C.insufficient piston lubrication
D.all of the above

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A.natural aspiration
B.masked intake valves
C.air cells
D.scavenging air

A.excessive lube oil consumption
B.lower than normal lube oil temperature
C.higher than normal exhaust back pressure
D.excessive crankshaft end play