You only worry when a 2 stroke QUITS smoking!
Agree with all the above though, probably summer storage. Also, if the sled has been started numerous times and only run for a short time (minute or less), they tend to build up oil and gas, and will smoke A LOT until its all cleaned out. This is really common on a sled you just bought, as he probably showed it a couple times, starting each time for a little bit.