I recently purchased a 2003 KTM 450 EXC. My understanding is that the stock carb is an FCR MX39. I went to pull out the Power Now off a 2005 WR450 and place it intothe KTM. The KTM carb opening was too big. I thought both bikes have the same carb. How can I tell which carb. (maybe the FCR MX41) I have on the KTM. Does the serial number on the outside give any clues?