Hope you’re doing this with a chain on so you can slow the engine down with the brake. Try loosening the clamp holding the carb to the rubber boot and pull the carb. Check the boot for cracks. While the carb is off, find out the size of the main jet.
There are two adjustment screws on the carb, the throttle stop screw and the air screw. Turn them both of them gently in until they stop. Open the throttle stop screw (the top one) a half turn. Open the air screw (next to the fuel line) two turns.
Since you said your were no to karting; is there oil in the gear case and how many onces of oil are you mixing with a gallon of gas? And is there any chance you have a tach to hook up?
One last thought for now, is there a spring above the slid in the carb?
LAD Specialties customer / tony kart / rotax / kt100