I remember seeing that advert at the pictures before the start of a movie ( made me want to mono my 1979 yz80 everywhere) . From memory it was a 1978 xl250s , because all the young louts around town ended up buying these xl,s instead of cars and causing havoc by mono-ing everywhere.The add was a definite success,(probably what the yamaha wr250 advert of a few years ago was based on) being screened continuously on TV CWN-8 orange at the time.
Maybe the ad can be found at the film & TV archive in Canberra or the Prime TV archive......