A retired military mechanic is removing a cylinder head from the motor of a Harley motorcycle when he spots a well-known heart surgeon in his shop. The mechanic shouts across the garage, "Hey, Doc, can I ask you a question?"

Surprised, the surgeon walks over. The mechanic straightens up, wipes his hands on a rag and asks, "So Doc, look at this engine. I open its heart, take valves out, fix them, put them back in and when I finish, it works just like new. So, how come I get such a small salary and you get the really big bucks, when you and I are doing basically the same work?"

The surgeon pauses, smiles, leans over and whispers to the mechanic, "Try doing it with the engine running."