ok, when was the last time you cleaned the carb?
HOW long does this atv sit between being used, IF over a month or so
MY suggestion is this
DRAIN fuel, inspect tank, MAKE sure its CLEAN
then clean/rebuild carb
if you clean carb and have a dirty tank, as soon as you run fuel back into carb, you can have a dirty carb again, thus why I said, START a new, new FRESH fuel(non ethanol all the better) then clean carb
check and inspect your choke cable, and make sure its working properly, a stuck chom=ke can happen and cause both starting and running issue's
as can a stuck float flooding your motor
NOW< that I said that, ITS time to check your OIL and SMELL it
if it smells like fuel, you have a carb problem and most likely a stuck float
Having fuel/gas in your oil is BAD< you need to fix this ASAP< and or at least, shut fuel peacock OFF< drain carb bowl, and then change oil and oil filter!
fuel in your motor will make seals and things go dry and or rust, causing failures and bigger issues for you!
NOW< IF your carb is 100% correct, fuel in GREAT and fresh
you can have other issue's,
from jumped time, to a BAD CDI, low compression, , even a BAD spark plug(easy one to fix, and won;t hurt if you put a new one in gaped right, and inspect the old one and see what it says(tells you by looking at its color)
OR post a pic of it here?
but the above is all good places to start here for you, and not so hard to do