A guy walks into the local hardware store and asks for the best chain saw they got. The salesman tells him, "This is a real good one, and it can cut 10 cords of wood a day."
So the guy buys it. He goes right home and starts cutting. He cuts all afternoon and in to the nite. At dusk he only has 1/2 of a cord cut. So he figures he'll really give it a go and try again tomorrow, to see if he can cut 10 cords.
Well, the next day comes and he gets up early and cuts all day, even skips lunch. This time dusk comes and he only has 1.5 cords cut.
So the next day he takes the saw back to the store and complains. The clerk says, "Lets take it in back and check it out." So they go in back and the clerk starts it up. The guy jumps back and says, "What's that noise?"