First of all I live in Southern Saskatchewan, Canada. I got the bike in late summer when it was just starting the cool off. On some of the colder days it was hard to start (took several kicks with choke on). It is now starting to be winter. It is currently -11 degrees Celsius ( 12 degrees Fahrenheit) and i can not get the bike to start at all. As far as I know the jetting and everything else is stock. My bike is a 2003 450 (was told it has very low hours on it). I am running 10w50 oil I believe. (i changed it a month ago and that's what the dealer suggested i use in it). the only mod that I've done was changing the exhaust out for an exhaust off for a YZF exhaust (quieter than the gutted wr exhaust and performs just as well). I would like to be able to ride my bike during the winter but it won't start. Do I need to rejet? If so what jetting should I get? Should the same jetting for winter work for summer seeing as it was hard to start sometimes during the summer too? I was thinking about taking it to my dealer and getting them to look it over (change my fork seals, clean and tune/jet the carb, check valves).