$3000 for a bike that's not running is a little high.
He's not going to get that for the bike from anyone else. I'd say you should offer him around $2500 for it. I wouldn't really spend more than that. If it were a newer 955i, it might be worth $3k, in non-running condition but I just can't see him getting $3k for that bike, while it's not running.
If you buy it, you're going to have to put about $500 into the bike anyway. New tires, fixing the electronics, cleaning it up, other odds and ends, etc... You could tell him that he can do all that stuff, get the bike running and then you'll give him $3k. Otherwise, $2500 is fair because you're going to have to do all this work just to get it roadworthy.
IMHO...
