Hi, I was wondering what type of engine is the most reliable/toughest? What I mean is that it won't blow up quickly and won't need replacement parts fairly quickly. I have a 2002 Yamaha YZ250F and I don't ride it extremely hard. I don't hit the rev limiter or anything and I've put about 20 hrs on it from the 20 it had from the previous owner. Its been a great bike. Anyways, I was looking at RMZs and KXFs and I've heard that the Yamaha YZ250Fs are more reliable. What are your opinions on types of engines?