i would check the swing arm and rear sub frame on the zzr but as already mentioned i am going on hearsay,if looking at thundercats then check second gear by riding in 2nd and accelerate hard right up to the red line,if it jumps out of gear then walk away from it,also shop around as you can get bikes in that price range with quite a few accessories,ie.stainless exhaust,crash bungs,braided brake lines double bubble screens and so on
..........................Sam