Hi all. Small problem with the bike that has arisen in the last couple of weeks. It usually idles around 1500 rpm. But sometimes when I pull up the at the lights it will sit at 3000 - 4000 rpm for 30 seconds to a minute, then drop back down to normal. Is this a cold weather thing, or do I have a problem? I know i'm not leaning on the throttle or anything, and the choke is not out.