My 2 stroke 50cc atv will not start without choke ,when I start on choke it runs ,when I turn choke off continues to run so I leave it to warm up and when I turn it off it will not restart without the choke and also sometimes while running there is air coming out of the air intake, is this normal if not how can I fix?

 

I'd clean the carb.
Some blowback can be normal but while the carb is off, inspect the reed.

 

it's a duece so reeds may be shot or rings you got to do a compression test. then check your carb but I'd make sure the gap is correct in the plug as well.