I'm trying to fix my son's go kart that me ex bought him.It keeps throwing the drive chains off.Engine is already adjusted all it can go,who sells the sprockets and chains for these?The main drive sprocket looks weird,the teeth look cupped out and bent but I'm wondering g if the teeth are supposed to be that way?It's the manco 126cc interceptor kart.Any help would be great,it also keeps stalling ,I can mess with a little black plastic piece on carb and it stutters and stalls..Hmmm