i have a 2009 atomik motox 125cc and no probs so far but i have noticed a scraping noise when moving the end cap was falling off the exhaust but that is fixed and i have no idea what it is
baffle could be loose inside the muffler.
bashplate could be loose or cracked.
could be heaps of things but those are the common ones and are easy to check
well grease up you bearings and see if it goes away, I had a similar problem I thought was the motor grinding going over bumps, turned out my swingarm bearings were rooted