My first bike was a GN250.....bit older than yours, though! Mine was an '85 model with?????kms on the clck. A very good family friend found it for me at the rock bottom price of $750 on-road 7.5 years ago. Needless to say, it lasted just over 3 months before I blew it up halfway between Melbourne and Phillip Island! It was a good bike, but I don't think it appreciated having its neck rung at high speeds! I don't know if that's a GN specific thing or whether it was my poor, abused bike's thrashed engine that just gave up the ghost! Do you have the owner's and service manuals for it?