I have owned my 1300 for about a year now and recently when I was riding it I went over a bump and grinding type noise was heard in the bottm end. The noise went away in about 5 seconds. I felt something clanking against the engine covers back and forth. The bike still runs fine. I dropped the oil pan and found a plastic washer type object in the oil pan with the number 15 molded into it. It is a hard plastic black in color about an inch or so in diameter. Does anyone have a clue as to where this came from?