Yep... Bring something out and run it. That's about what it comes down to.
ljHall09-- What's up bro! That was Logan Karnow on the KLX140 at the Medina Fair. The kid can go lightning fast on anything. If you put a mere mortal on the 140, they wouldn't do nearly as well. I used to have a slightly Modded 110 that I used to race in the Vet classes. I always thought 12 inch wheels was the way to go too. I just happened to have a 150F sitting around that I was planning on using the motor for in a different project. My 110 had a flat tire, so I brought the big slug 150F out to the track just to fool around with. It was so much fun, and so cheap-- I sold my 110 and just ran that. I know what you mean by pit bike, but pit bikes USED to be stockers with big bars and tall seats. Now that we're running Mod bikes on big bike tracks-- it just makes sense to ride the bigger trail bikes. It makes even more sense money wise. I don't care what they call my bike, or the class it races in-- I just call it cheap fun!
I think the AMA races that you're referring to are the "Pit Bike Nationals". As far as I know, they don't have them any more. I'd disregard the rules-- pick a bike that suits your local riding spot (The place you'll be riding it MOST often)-- and have a good time. Tune in to Planet Minis. There's a new CRF110 coming out that looks to be pretty cool. Check it out! --L*64