Allan, a mechanic, was removing a cylinder head from a Harley-Davidson motorbike, when he spotted a world-famous heart surgeon in his garage. The heart surgeon was waiting for the service manager to come and take a look at his bike.

Allan shouted across the garage, 'Hey Doc can I ask you a question?' The famous surgeon, a bit surprised, walked over to Allan. Allan straightened up, wiped his hands on a rag and asked, 'So Doc, look at this engine. I also can open hearts, take valves out, fix'em, put in new parts and when I finish this will work just like a new one. So how come I work for a pittance and you get the really big money, when you and I are doing basically the same work?'

The surgeon paused, smiled and leaned over and whispered in Allan's ear, 'Try doing it with the engine running.'