I know these beasts quite well.....pretty reliable usually with the above caveat...but check out a)is the engine original as they often get replaced b) what parts is it likely to need as some are cheap others pricey.
eg. I bought a basket case R90/6 over Christmas and need to repace the instrument housing....at £112 for the housing alone?
Though 'yours' should have the instruments in the headlight...
Good website for checking out engine numbers etc is BMbikes...uk based but with lots of helpful links
Al
