83 fourtrax wont run

Hi I own a 83 fourtrax 200 it’s been sitting for a while and now it won’t stay on it starts but does seconds after! I’ve cleaned the carb out I’ve cleaned the gas tank and it has a new spark plug. I don’t know what’s wrong but I am going riding next weekend and I need it fixed. Shoot me a text or email at 2067352282 blakelycolby@gmail.com thanks!