Despite all the rumor and other peoples thoughts, A B and C stood for 1st 2nd and 3rd generation of bikes in Hondas early years up to the late 50s.
It changed when the started producing the twin cylinder bikes and C stood for base model and CB was the sports version of the C model.
If I am not to be beleived, (as this subject has been around many times) just check it out for yourselves on Google images.
Search C92 and CB92...C72 and CB72...C77 and CB77. You will find that the C was a tourer or comuter and the CB was a sports model.
The A came in with the CA92, CA95 CA72 and CA77, these were the early base models for the American market and the specs differed from other world markets.
What didn't make sense was the fact that they dropped the A from the Sport models sent into the States and just called them CB92 and 95, CB72 and 77 like for the rest of the world.
The popular one in the States was the CA95 but the specs for this motor were nothing like the C95s that the rest of the world got.
Sam.