A friend of mine in the 70's had a Harley chopper that would take my Z1 900 for the first 50 feet. Man that thing would launch off the line but after the 50 feet I was gone.
Keep in mind that back in the late 60's early 70's the Harley Sportster was one of the fastest production bikes in the 1/4 mile. Harley just got left behind in the evolution of motorcycles. They were winners in flat track as well. The Sprint H was also pretty fast until Honda started to dominate the small cc field.