I have a 1974 Motoski Capri and it wont run.?

i need some suggestions on how to get my sled running i tried starting it it turned over so i put fuel directly into the carb. It starterd up but it was only runnin because of the gas in the carb and it ran for 4 seconds then died out. i no its not the fuel line cuz i just replaced it any ideas on wut it might be.