I have a 2002 Polaris 600 XC. It is new to me this year, but has 1600 miles from the previous owner. I went through it completely this year and cleaned the carbs, the valves, etc.. The one issue I have is that when you come to a standstill after riding a little, the engine will idle at 4,000 rpms for 3-4 seconds before gradually settling down to idle at 1800 rpms over the next couple seconds. Is this normal? Is something dirty or out of adjustment?