I just bought my bike and it´s got 17K on it and seems to be in pretty good shape overall. After two days of riding though, I noticed that there is a rattle sound coming from the chasis when I´m in second like something metallic is rattling inside. There doesn´t appear to be a performance issue as it rides good and continues accelerating, but I need to know what this is and is it safe to continue riding on it? I hear this in every gear, not just a specific one. Any thoughts as to what this could be?