Well, the last year in which the old Spa ciruit was used for the motorcycle belgian GP was 1978 (last year for F.1 car GP: 1970). In 1977 Barry Sheene lapped it at an average of 137.15 mph. This still is - and it will remain for who knows how much time! - the fastest lap in motorycle GP history. Actually the fastest track used for motorcycle races is Dundrod.

Incidentally, Jo Siffert lapped the old Spa circuit in 1971 on a Porsche at an average of 162 mph!