Mechanic And Doctor

A mechanic was removing the engine parts from a motorcycle,when he saw famous heart surgeon in his shop.. He called the surgeon n said.. "Look at this engine... I opened its heart,took the valves out, repaired and put them back"...So why do I get such a small salary and u get such a huge sum.... The doctor smiled at the mechanic and came close 2 his ear and said.... "Try the same when the engine is running.".