Gary says in his book that he has heard many rumors of chain drive, but they have all turned out to be "a later, home adaptation". He goes on to say that according to plant/production manager Stan McCarthy, Simplex did build 1 test bike with chain drive with a Villiars engine around 1947. Stan's opinion was it was superior to the simplex powered machine, much faster, at about 55mph, but was deemed unsafe by J. Paul Treen.