This website talks about human powered bikes reaching over 65 mph! http://www.wisil.recumbents.com/wisil/whpsc2007/speedchallenge-2007.htm
The current record is 82.3 MPH. There is hope of breaking the 100 MPH mark this fall. We'll see. One of my many other interests is human power vehicles. I don't do the speed racers, but I invented an arm and leg powered recumbent that is capable of increasing the power by 60% in a sprint and about 25 to 30% in a normal ride and on long rides of 100 miles or so, you finish much less fatigued because you share the work load between the arms and legs. Plus you get a full body work out. Google "Louis Hudgin recumbent" for more information. Louis