First Blaster

That's a very fair price for me, I'd go for it if was looking for one.
Looks like you'll need new rubber but find out how much life is left in that cylinder!
 
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.