looks good, all stock, so try to get him down a little, and start it up and try to get him to let you ride it, if somthin doesn't feel right tell him, also if you can, get a mechanic to come with you to check it out or have the guy meet you at a dealership to get it checked out, if the engine maked weird sounds or is bored very far over think again, i bought mone with a tocking engine, and it had to be rebuilt, i got cheated. also, ask lots of questions, and thourogly look at it, and make shure it is all in proper order, things won't be perfect for 850 but it shou;d work well, and drive well, look at the case by the sprocket and make shure its not cracked, if i missed anything, the others will tell you.