yes you need to rejet for the colder weather.. you prolly have a fmf so summer you should have around a 260 main ,so winter try around a 300main and see how she does always good to start rich..
http://jetsrus.com/main_page.htm i wouldnt just buy a 300 i would buy some smaller and some bigger 1s this way when it gets warm again you have the extra jets on hand ,..