Last weekend i was out with the revo when i noticed the engine sounding rough .This is the third engine that ive had now and in each case the rear bearing has failed.Why are these engines so bloody expensive any way?IM going to stick to the 2.5 engine as the one in my jato is going strong after 2 gallons.Has any one else had this problem as when i told modelsport they said it was a new one on them.