I haven't had any issues so far up until yesterday, running hard it runs great, when you let off the throttle it backfires, spits sputters, and dies. It starts right back up no problem. Any ideas on what could be the issue, I am thinking one of the jets is clogged with dirt or something. It probably just needs a good cleaning. This happened all of a sudden. The quad had no issues prior to this. 2013 450r. Any ideas would be greatly appreciated.