welcome to the site
NOW< some more info
how often do you use this atv, does it sit a LOT
if it sits a lot, its very possible your fuel is BAD, ethanol fuel can go bad in a few weeks
maybe start with draining the tank, make sure its clean inside too when drained
then check and make sure your fuel peacock is working and flowing well
NEXT< if it was me I would replace fuel line from tank to carb, cheap easy way to know fuel line is clean and not varnish coated!
THEN< its time to clean your carb, as sounds like you have a fuel supply issue, and by cleaning tank, peacock,line and now carb, then starting with new fuel,
you rule out all these issues as possible causes to your problem!
and most likely will resolve your issue in the process
also, if this atv sits often, I HIGHLY suggest buying NON ethanol fuel for use in and and TREAT IT as well!