Also look at $$$. The money you can save buying used compared to new can actually get you an advantage over new. For example, take the money you saved and upgrade to ceramic bearings...maybe upgrade from a Saturday motor package to an Elite or Champion motor package...maybe get an extra set or 2 of tires to help throughout the night when conditions change...get a better rolling chain...free floating hubs...upgrade to that better clutch...so on an so on. Look at upgrading safety as well! Better helmet, better racing suit, better neck bracing system. I'd be more worried about the guy that shows up with a used chassis that has money invested in it to make it super slick over the new chassis showing up with basic setup components.
I've seen guys spin axels that just don't ever stop because they took the time to invest in good quality parts with the money they saved buying used chassis.......rumor has it those karts are sitting in a barn somewhere collecting dust but the axels are still spinning to this very day