I'm new, names Jolene, Hello all.

I just bought a 50cc Grunt 4 stroke for my son and like all complaints, we drove it very little over two days and then it wouldn't start. I did the carb yesterday and I'm pretty sure there is no spark. I checked it the same way I do my truck, pull the wire off the plug, stick a nail in it and hold it up to the metal. Correct?? I'm going to check the soilnoid, starter, screwdriver test today but I figure while I'm messing around I'll change the plug. So what is a compatible japanese plug that will work wonders on a chinese atv? Can I get parts for this beast at a Part Source? What type of Soilnoid, stator and coil should I use? What is a CDI? LOL
I thank you all in advance.