How do you get a Wildfire 49cc dirtbike started?

I purchased a Wildfire 49cc Dirtbike for my 8 yr old son for xmas. soon after we started it once and let it run briefly. now that the weather has broken i have tried to get it running to no avail. i've changed the spark plug, changed the fuel (w/proper mixture), and adjusted the idle screw. Any suggestions?

try taking off the carb and cleaning it, when gas sits for to long it goes bad and can even get kinda goopy and wen it does it will plug up ur carb and if its a two-stroke and the gas is all ready mixed it will go bad even faster, that's why whenever your not gonna be riding your bike for awhile you should drain the gas then turn the gas off and let the bike idle until it dies so that all of the gas gets flushed out of the carburetter, if you don't know how long it will be until you ride but it might be soon then just do the same thing only don't drain your fuel, but you should all ways turn your gas off and burn the gas in your carb when you done riding for the day