I have read through several threads with somewhat similar issues, but I am unsure if that is what is going on with my bike, or how to troubleshoot to rule things out.  I have a 2013 s40, only been riding  for 3 weeks, but up until this past weekend I was not having any issues.
The first time it happened was this past Friday, a colder morning than what I had ridden before, early morning temps down in the 50's but in the mid 60s when I went out.  Started with the petcock on prime, choke out, let it warm up maybe 5 minutes as I forgot something inside. Once warmed up, switched to on, choke in, and took off. First intersection i came to, I am in 1st, and I stall. I figure I am new and just didnt give it enough throttle, so I start up again and go on. But it happens again two more times as I am slowing down at intersections. The third time it doesnt want to start up again. I give it a couple tries, and am able to get it to start, but I let it sit for another 5 minutes to be sure. get going again but stall 2 more times, both when slowing down at intersections.  At this point I was advised to adjust the idle speed up, but only a little bit.  So I did, about a quarter turn. Stalled one more time, this time slowing down into 3rd. So i did another small turn, and got the rest of the way into work, without a stall. The day heated up, near 80. When I left work I stalled again twice at the very start of my ride. The next day, within the first mile, I stall at an intersection. So I switched it to Prime and didnt stall again the rest of my ride. the next day, same thing, regular start up in prime and choke out, switched to on for ridding and a stall withing the first mile. switched back to prime, and no more stalls. Does this sound like the vacuum petcock issue that seems common, or am I idling too low? are there other things I should check for?  

Versy,
Nailed it again.