check the quad over well. If the quad looks beat it probably is. Check all the things that are going to cost you a bit to replace if they are borken. ie tires suck to have to replace rite away, shot bottom end, bad tranny, top end rebuild. Small problems are ok. Then check it over for cracks in the frame and such....Just look it over. we all know what a good quality bike looks like and what crap looks like.