I dunno-- ya may have a deal with that '85 CR. It looks pretty nice. Hell-- for another 200 bones, I'd take the '94 as well. You can find the parts on Ebay to spit shine the 'ol '94 right up. That '85 would be a strong competitor in the above mentioned vintage races. I don't believe they had magnesium engine covers in 1985. I think that was a 1983 problem only. You should be able to get $1000 for the YZ85 on Craigslist if it's as nice as you say.
If you have an interest in vintage then grab 'em up. If you're just looking to get a bike to ride-- you can do alot better. Pit has a '92 RM125 in boxes that I know he'd sell ya for what he has in it. Probably around the same as the '85 CR. Suzuki is a ton better for parts availability than Honda. I'd say that Honda is actually the worst in that respect. You can get a decent 125 from the last ten years for around $1000. Then figure on another $500 in chain, sprockets, tires, fluids, top end, etc... good luck, and watch craigslist. --L*64