Polaris rzr 170 troble

Hi
i live in sweden and my son have a polaris rzr 170 and it will not start it just starts up for one second or two, i have checked the the ignition and it has a blue spark, i have cleaned the carburator,disconect the brake sensor and jumped over a cable on it,the carburator have fuel so i dont think it is the fuelpump, so now my ideas are empty so i try to write on the forum for any help.
My english is not perfect but i hope you understand :):)