Check the fuel pump to make sure you get enough pressure and it's in good shape and not leaking. Check around the airhorn and entire carb to make sure you don't have any cracks. Ensure your vacuum hoses are connected properly and your timing is correct. Connect a vacuum gauge and and set the mixture screws to about 2 1/2 turns out from fully seated. Watch this video: https://www.youtube.com/watch?v=HKGqKZsf3cc