Popping sound in exhaust

Update:

I got the initial timing down to 12* BTDC. I had to fiddle with the mixture and idle speed screws to get it to not load up. I'm thinking that the throttle blades were open too much but I couldn't turn speed screw down. What I ended up having to do was turn the mixture screws all the way in. The engine sped up then I turned the speed screw down to bring the idle back down to ~750. Then backed the mixture screws out till the engine sped up and then backed out the speed screw. Eventually I got it to idle where it will die if I close the mixture screws. It likes it best at about 3/4 turn out.