Why would my Cruzers turn a rustygold after only a couple hundred miles? not the heat shields but the actual pipes, only have 200-300 miles on them. I have been told that it is from running to lean(according to mfg's) but at the same time no rejetting is necessary per the online boards and local bike wrenches. Carbs are adjusted properly. Funny thing was that it is the right side discoloring but the left side was popping(solved that a 100 miles ago) which meant it had been leaner and hotter.