All my friends that have raptors, always have have some problem with it, and they were the ones giving me shit for getting a banshee, because of how unreliable they are. pffft, I'm the only one who can go riding at any given time, because my quad RUNS. No problems yet...knock on wood
Loganskinner, it sounds to me, like something was too tight, and as the engine warmed, got even tighter, or something was floating around loose in there and got caught up in the timing chain or something.