The cardiologist and the mechanic

A mechanic was removing a cylinder-head from the motor of a Harley motorcycle when he spotted a well-known cardiologist in his shop.
The cardiologist was there waiting for the service manager to come take a look at his bike when the mechanic shouted across the garage " Hey Doc, want to take a look at this?"

The cardiologist, a bit surprised, walked over to where the mechanic was working on the motorcycle. The mechanic straightened up, wiped his hands on a rag and asked, "So Doc, look at this engine. I open its heart, take the valves out, repair any damage, and then put them back in, and when I finish, it works just like new. So how come I make $ 39675 a year and you get the really big bucks, when you and I are doing basically the same work?"

The cardiologist paused, smiled and leaned over, then whispered to the mechanic... ''Try doing it with the engine running."