When cold you will need to choke it by covering the airbox tube to richen the mixture. Also the added vacuum helps get the diaphragm in the carb pumping fuel as well. Dont give it any throttle until after it fires, this can take more than a few seconds when you first get to the track, after it has been running it should fire right up but still dont give any throttle until after it fires.
You might need to adjust the carb, A good starting point would be 1-1/4 to 1-1/2 turns open on the low needle and 1/2 to 3/4 on the high.
Also the carb should be cleaned regularly, dissemble the carb completely and clean the carb and all passages with carb cleaner, just carefully wipe clean the rubber parts, inlet needle and pump diaphragm. Clean the inlet screen and reassemble. There are some videos you can watch to learn how to do this.
Idle once warm should be high probably over 3000 rpm if it will idle.
You need to clean the plug if its a new driver and they aren’t driving hard at full throttle for most of the lap. An abrasive plug cleaner is recommended from aircraft spruce or harbor freight tools. Use a BR9EG when its not being driven full tilt and especially when outside temps fall below 75 degrees. A BR10EG is recommended for 75 and above when you are driving it hard.
It is normal for it to want to stall when coming off the track.