I cleaned up my Nephews 93 XR 80 for him over the winter. I replaced some parts such as the tires, chain & sprockets, grips, etc. I noticed when the bike idled at a very low rpm there is a rattle in the head. I can't hear it if I turn up the idle. The first thing I thought of is piston slap but the bike doesn't appear to burn any oil. It is still pretty snapy and runs good. Started on the first kick after sitting all winter. My nephew bought it last year and it appeared to have the stock tires and sprockets on it, though they were hosed. I tried to find an XR site like this one to ask this question with no luck. Is this normal for an XR at very low rpm? Has anyone experienced this?