I'm wondering where you got the gas to fill up that brand new tank with. New tank, new carb, new motor, none of that's going to matter if you pour shellac into it. That can of old lawnmower gas (hopefully not mixed 50:1 with 2-cycle oil) that hasn't been completely empty in years, just topped off sometimes, cannot be depended on for anything. If that's where the gas came from, how do you know it had fuel stabilizer poured into it every time it got new gas?
Start with a clean slate. Get a brand new gas can with a cap you won't lose and have to substitute for with a rag stuffed in the hole. Measure how much REGULAR gas you put in the can. Then follow the chart on a bottle of Sta-Bil or similar stabilizer, and put that much in the can and shake it around BEFORE adding it to the kart tank (having emptied the tank before you do). Label the can as "89 octane kart gasoline only".
Loosen the bolt head on the bottom of the carb bowl and drain it of old gas.
Find the (black plastic?) screw that pushes on the throttle above the carb, that's your idle screw. Run it in clockwise enough to see it move the throttle some. Then LOCK DOWN the kart before cranking. That higher idle that helps it crank might engage the centrifugal clutch and get it running down the street. After running over the dog. And the kids.
