To specifically answer, no, I don't think there's a place on the web where you can get a set of the rules. The sanctioning bodies sell the rule books as a major source of income - so they do not put the rules on line. You're welcome to ask specific questions here, and you'll probably get answers. Yes, it's confusing to someone that hasn't spent countless hours going through the rulebooks, especially considering the differences in the way car classes are printed and the way bikes are classed. But once you get the basics it becomes very easy.
Basic: Car class designations begin with a letter that designates engine size - with AA being the largest engine class and K (or maybe it's L) being the smallest. Bikes start with 50 cc and end with "over 3001 cc". Bikes engines in SCTA/USFRA rules are the same whether 4-stroke, 2-stroke, or rotary, while the ECTA has separate classes for each of those three.
And on and on. Order up a rulebook and start learning, and once you've got a little of it down pat -- ask for more help from us, okay?
