250 really isn't bad. As long as it's under 260ish, you should be fine. The largest and most prominant adjuster(should be sticking up and an angle from the carb) is the Primary Mixture setting. There should be a small one on the throttle side, that's the Bottom End, or Idle Adjustment. Clockwise is richer, counter is leaner. Richer is cooler and slower, leaner is faster and hotter.
Sorry about the instructions comment, we have a TON of kids come on here, and ask for directions that came in their box...
