Hey flkid, congrats on the score. Your kart looks like a 1990's model and its value would probably be $500 or so when running or maybe $300 or so as-is. It probably cost a couple grand when new. (that's without an engine)
Its usually difficult to ID the brand of race karts cause most look very similar to each other and dont have the brand name printed anywhere, but they all should have came with a serial # stamped into the frame somewhere. A few clues that can sometimes help out is the location of this serial # and other small details that usually vary from brand to brand. (check and see if most all the karts nuts and bolts are American or Metric too)
Most all race kart brands were very high quality and lots of parts interchange between brands but If you still want to ID. it: You'll probably need to take/post several more pics of the kart showing the rear frame/axle section, front of frame, spindles, bumper area and the steering column support area. After draining the oil, you could also stand the kart upright and get a good pic of the whole bottom side too. Then If nobody here knows you could post your pics on a race kart forum like bobs4cycle.com. Someone over there would know what you got there for sure.