Just got a new 2013. I have about 100 miles on it. I noticed the engine does not idle down properly all the time when the throttle is closed. It hovers a few hundred RPM above idle for about 20 or 30 seconds and then idles down. Sometime it does not idle down at all. Just incase the dealer put shitty gas in it I have been topping it up with Shell 91. Any idea what it could be? Shitty gas? Not enough freeplay on the throttle, sticky carburator, etc. Any input is approciated.