as ptlcb1 says,
the CB400F is the original 70's bike.
it is an aircooled parallel 4 cylinder 2Valve SOHC Engine with ca. 37 BHP.
The F stands for FOUR,as in 4 cylinder.
was an amazing bike and one of HONDA's greatest achievements.
still a fair few about,now.
here is a Wiki link:
http://en.wikipedia.org/wiki/Honda_CB400F