engine don't keep running after start

[jdpalmer]

Checked all electrical and timing several times. Used small gas tank to eliminate fuel not getting to carb. changed from zenith toTillotson to Zenith. Starts good but dies in few second. Can pull choke when dying and will ruin a little longer by this it run about 60 seconds then backfire loud and quits. Help I feel like I've tried everything and I've worked on A's for 20 plus years. still don't know it all