There are different kinds of care given to machine parts. Technician A says that a pilot bearing should always be replaced when a clutch is replaced is a true statement and thus is the only correct one.
Most times, pilot bearing is often replaced as kind of precautionary measure that is taken when clutch is replaced.
Torsional vibrations are said to be vibrations due to firing force twisting and accelerating of the crankshafts when a cylinder fires and cannot be absorbed by oft-dampened clutches.
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