Howdy - and welcome to the Forum. What name shall we call you?
As for your question -- go ahead and order your rulebook right now. That way you'll be able to have it available when you ask a question and one of us tries to help you. We can tell you something - and tell you to look on page such-and-such for the complete rule.
As for the Fazer (if you're planning on running it) -- the various classes allow no modifications from stock (save for a few safety items), basically stock bodywork and frame but much more in the way of engine changes and stuff like that, or darned near anything goes (in the "Altered" a/k/a "Special Construction" class. The engine size determines which engine class you're in, simply put. And then you decide if you're going to run in "gas" class, which means on fuel you buy at the event, or fuel class -- which allows you to use anything, from somebody else's (other than ERC, the event fuel vendor) stuff to bug juice to nitrous oxide - and so on.
Think of the class designations as a good effort to make sure you're running against other bikes that are pretty close to yours in modifications and engine size. Potentials are something else, of course. And finally -- you must consider, when choosing classes, that you must build to the speed of the record in your chosen class. Mostly this affects safety items - but might include other stuff. You'll have to ask on this one - but if you say "The record in my class is xxx, but there's no way I'll go that fast - I just want to get a taste of the speed" -- no, it doesn't work that way. You must, I say again, build as if you were a legitimate contender for the record in your class.
Okay - get your rulebook on the way and ask away.
Regards,
Jon, owner of landracing.com, also known as Seldom Seen Slim