the poping through the carb means way out of time. Did you pull the dist and turn the crand 360* as stated above?? That is for when you change timing chains and sprockets.. If you did that then your timing sprockets are now 180* out. bring things back to TDC and Take out dist and spin crank one more time 360*, put dist back in. If you turn the crank eirlier, your dist is put in correctly but your timing gears are now 180* out. You didn't change chains and sprocket when you started all of this did ya? If not, then do this and see if it starts.
If you are by yourself, you can loosen the spark plug about one turn mayb less and bring the engine around manually and you will hear the compressed air escaping between the threads of your plug. When you hear the air escaping look at your balancer and line the marks up to 0. then pull dist and rotate motor and put dist back in. "DONT USE THE KEY TO TURN THE MOTOR"