I have a 1999 Kawasaki Prairie 300 4x4 ATV that I bought used last summer. I haven't run it much lately, although the last time I started it about 2 weeks ago it started fine. The ATV is garage-kept, with the temperature getting down to about 45 degrees. I tried to start it this evening, and it won't fire. When I choke it and try to give it gas, igives out a huge backfire but won't fire or turn over. The gas is fresh. Is there a trick or something I should be doing in cold weather to get it going?