In my experience, cold usually means electrical issues. I had a similar problem with my Aprilia. Turns out the sparkplug boot eroded and wasn't providing enough spark to get it to kick. Once it did start, it ran fine, but I blew up way too many starters. I use lots of dielectric grease on my plug boots which usually helps. You can always use a screwdriver to ground out the boot against the engine or frame to see if you are getting spark. If you aren't, trace the wiring back. If you are getting spark, it's likely fuel not getting all the way to the cylinders for some reason. Also check the start/kill switch to make sure its not intentionally killing the engine. Those are the first things I would do.