Short of a teardown I don't see how the buyer of a second hand motorcycle would have a chance at spotting such a fault without driving the bike. And even a teardown might not show the fault, in fact could make it worse.
That's equally true for an aeroplane engine - the difference is that no pilot would skip performing maintenance at the required intervals and there are maintenance logs etc. in place to enforce this. What makes the Cessna engine more reliable than the motorbike engine in practice isn't a simpler design but a better maintenance and operation culture.
Sure. But the accepted norms for buying second hand aircraft versus second hand motorcycles are quite different as well, which is why it makes no sense to say that the buyer should not have driven the motorcycle. The accepted norm for cars and motorcycles is that you pay the seller and you drive them home, not that you inspect the detailed maintenance log or do an on-site teardown. Likely the seller was aware that this bike had problems and simply did not tell the buyer, something that is close to fraud, and on top of that this placed the buyer in a potentially dangerous situation, especially on a new bike.
When I buy cars I do a pretty thorough inspection and an extended test drive. Even so I once ended up with a car on which the clutch pedal would not return once every few hundred strokes or so, something that by chance did not happen even once in a pretty long test drive.
