I have a yz125 now and after riding at some trails i realized it doesnt have enough power for me i am 6'2 190lbs. I have decided to buy a new bike but im not sure what to get. I was thinking of a 250 two stroke, 250 four stroke or a 450. I just need something with some bottom and mid range power. i have heard of people blowing up four strokes and spending $1500 fixing them and since i am buying used i want to avoid that. I was just wondering what you guys thought would be a good bike for me and if it is common to rebuilt used four strokes and some other things i might run into. Also if you could give me some advice on buying used.